Alright, this should work. This is an example of a working Rmd file:
---
title: "Untitled"
output:
pdf_document:
template: template-sep-refs.tex
citation_package: biblatex
includes:
in_header: header.tex
bibliography: [refs.bib]
---
Here is a domain-specific reference [@eddelbuettel2011rcpp], and here is an R reference [@R-ggplot2].
Here is another citation [@R-knitr], and it will show up in both reference lists.
# Domain References {-}
\printbibliography[category=domain,heading=none]
# R References {-}
\printbibliography[category=R,heading=none]
You can customize the different reference groups in the file called header.tex which should be in the same location as the Rmd file. It contains:
\usepackage[style=numeric,backend=biber]{biblatex}
\DeclareBibliographyCategory{domain}
\DeclareBibliographyCategory{R}
\addtocategory{domain}{eddelbuettel2011rcpp, R-knitr}
\addtocategory{R}{R-ggplot2, R-knitr}
Play with this as you wish to choose the citation style, and also to set up the different categories, and which citations belong to which category. The \addtocategory function can take a comma-separated list of IDs like \addtocategory{R}{ID1, ID2, ID3, ...}. Note: A bib ID can belong to more than one category, if you want to it to show up in both reference lists, for example.
Lastly, you need to template file (template-sep-refs.tex). This is the default LaTeX template for R Markdown (found here), I just commented out some lines (lines 380-388) to make this work. Place this in the same location as the Rmd file.
% Options for packages loaded elsewhere
\PassOptionsToPackage{unicode$for(hyperrefoptions)$,$hyperrefoptions$$endfor$}{hyperref}
\PassOptionsToPackage{hyphens}{url}
$if(colorlinks)$
\PassOptionsToPackage{dvipsnames,svgnames*,x11names*}{xcolor}
$endif$
$if(dir)$
$if(latex-dir-rtl)$
\PassOptionsToPackage{RTLdocument}{bidi}
$endif$
$endif$
%
\documentclass[
$if(fontsize)$
$fontsize$,
$endif$
$if(lang)$
$babel-lang$,
$endif$
$if(papersize)$
$papersize$paper,
$endif$
$if(beamer)$
ignorenonframetext,
$if(handout)$
handout,
$endif$
$if(aspectratio)$
aspectratio=$aspectratio$,
$endif$
$endif$
$for(classoption)$
$classoption$$sep$,
$endfor$
]{$documentclass$}
$if(beamer)$
$if(background-image)$
\usebackgroundtemplate{%
\includegraphics[width=\paperwidth]{$background-image$}%
}
$endif$
\usepackage{pgfpages}
\setbeamertemplate{caption}[numbered]
\setbeamertemplate{caption label separator}{: }
\setbeamercolor{caption name}{fg=normal text.fg}
\beamertemplatenavigationsymbols$if(navigation)$$navigation$$else$empty$endif$
$for(beameroption)$
\setbeameroption{$beameroption$}
$endfor$
% Prevent slide breaks in the middle of a paragraph
\widowpenalties 1 10000
\raggedbottom
$if(section-titles)$
\setbeamertemplate{part page}{
\centering
\begin{beamercolorbox}[sep=16pt,center]{part title}
\usebeamerfont{part title}\insertpart\par
\end{beamercolorbox}
}
\setbeamertemplate{section page}{
\centering
\begin{beamercolorbox}[sep=12pt,center]{part title}
\usebeamerfont{section title}\insertsection\par
\end{beamercolorbox}
}
\setbeamertemplate{subsection page}{
\centering
\begin{beamercolorbox}[sep=8pt,center]{part title}
\usebeamerfont{subsection title}\insertsubsection\par
\end{beamercolorbox}
}
\AtBeginPart{
\frame{\partpage}
}
\AtBeginSection{
\ifbibliography
\else
\frame{\sectionpage}
\fi
}
\AtBeginSubsection{
\frame{\subsectionpage}
}
$endif$
$endif$
$if(beamerarticle)$
\usepackage{beamerarticle} % needs to be loaded first
$endif$
$if(fontfamily)$
\usepackage[$for(fontfamilyoptions)$$fontfamilyoptions$$sep$,$endfor$]{$fontfamily$}
$else$
\usepackage{lmodern}
$endif$
$if(linestretch)$
\usepackage{setspace}
$endif$
\usepackage{amssymb,amsmath}
\usepackage{ifxetex,ifluatex}
\ifnum 0\ifxetex 1\fi\ifluatex 1\fi=0 % if pdftex
\usepackage[$if(fontenc)$$fontenc$$else$T1$endif$]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{textcomp} % provide euro and other symbols
\else % if luatex or xetex
$if(mathspec)$
\ifxetex
\usepackage{mathspec}
\else
\usepackage{unicode-math}
\fi
$else$
\usepackage{unicode-math}
$endif$
\defaultfontfeatures{Scale=MatchLowercase}
\defaultfontfeatures[\rmfamily]{Ligatures=TeX,Scale=1}
$if(mainfont)$
\setmainfont[$for(mainfontoptions)$$mainfontoptions$$sep$,$endfor$]{$mainfont$}
$endif$
$if(sansfont)$
\setsansfont[$for(sansfontoptions)$$sansfontoptions$$sep$,$endfor$]{$sansfont$}
$endif$
$if(monofont)$
\setmonofont[$for(monofontoptions)$$monofontoptions$$sep$,$endfor$]{$monofont$}
$endif$
$for(fontfamilies)$
\newfontfamily{$fontfamilies.name$}[$for(fontfamilies.options)$$fontfamilies.options$$sep$,$endfor$]{$fontfamilies.font$}
$endfor$
$if(mathfont)$
$if(mathspec)$
\ifxetex
\setmathfont(Digits,Latin,Greek)[$for(mathfontoptions)$$mathfontoptions$$sep$,$endfor$]{$mathfont$}
\else
\setmathfont[$for(mathfontoptions)$$mathfontoptions$$sep$,$endfor$]{$mathfont$}
\fi
$else$
\setmathfont[$for(mathfontoptions)$$mathfontoptions$$sep$,$endfor$]{$mathfont$}
$endif$
$endif$
$if(CJKmainfont)$
\ifxetex
\usepackage[space]{xeCJK}
\setCJKmainfont[$for(CJKoptions)$$CJKoptions$$sep$,$endfor$]{$CJKmainfont$}
\fi
$endif$
$if(luatexjapresetoptions)$
\ifluatex
\usepackage[$for(luatexjapresetoptions)$$luatexjapresetoptions$$sep$,$endfor$]{luatexja-preset}
\fi
$endif$
$if(CJKmainfont)$
\ifluatex
\usepackage[$for(luatexjafontspecoptions)$$luatexjafontspecoptions$$sep$,$endfor$]{luatexja-fontspec}
\setmainjfont[$for(CJKoptions)$$CJKoptions$$sep$,$endfor$]{$CJKmainfont$}
\fi
$endif$
\fi
$if(beamer)$
$if(theme)$
\usetheme[$for(themeoptions)$$themeoptions$$sep$,$endfor$]{$theme$}
$endif$
$if(colortheme)$
\usecolortheme{$colortheme$}
$endif$
$if(fonttheme)$
\usefonttheme{$fonttheme$}
$endif$
$if(mainfont)$
\usefonttheme{serif} % use mainfont rather than sansfont for slide text
$endif$
$if(innertheme)$
\useinnertheme{$innertheme$}
$endif$
$if(outertheme)$
\useoutertheme{$outertheme$}
$endif$
$endif$
% Use upquote if available, for straight quotes in verbatim environments
\IfFileExists{upquote.sty}{\usepackage{upquote}}{}
\IfFileExists{microtype.sty}{% use microtype if available
\usepackage[$for(microtypeoptions)$$microtypeoptions$$sep$,$endfor$]{microtype}
\UseMicrotypeSet[protrusion]{basicmath} % disable protrusion for tt fonts
}{}
$if(indent)$
$else$
\makeatletter
\@ifundefined{KOMAClassName}{% if non-KOMA class
\IfFileExists{parskip.sty}{%
\usepackage{parskip}
}{% else
\setlength{\parindent}{0pt}
\setlength{\parskip}{6pt plus 2pt minus 1pt}}
}{% if KOMA class
\KOMAoptions{parskip=half}}
\makeatother
$endif$
$if(verbatim-in-note)$
\usepackage{fancyvrb}
$endif$
\usepackage{xcolor}
\IfFileExists{xurl.sty}{\usepackage{xurl}}{} % add URL line breaks if available
\IfFileExists{bookmark.sty}{\usepackage{bookmark}}{\usepackage{hyperref}}
\hypersetup{
$if(title-meta)$
pdftitle={$title-meta$},
$endif$
$if(author-meta)$
pdfauthor={$author-meta$},
$endif$
$if(lang)$
pdflang={$lang$},
$endif$
$if(subject)$
pdfsubject={$subject$},
$endif$
$if(keywords)$
pdfkeywords={$for(keywords)$$keywords$$sep$, $endfor$},
$endif$
$if(colorlinks)$
colorlinks=true,
linkcolor=$if(linkcolor)$$linkcolor$$else$Maroon$endif$,
filecolor=$if(filecolor)$$filecolor$$else$Maroon$endif$,
citecolor=$if(citecolor)$$citecolor$$else$Blue$endif$,
urlcolor=$if(urlcolor)$$urlcolor$$else$Blue$endif$,
$else$
hidelinks,
$endif$
pdfcreator={LaTeX via pandoc}}
\urlstyle{same} % disable monospaced font for URLs
$if(verbatim-in-note)$
\VerbatimFootnotes % allow verbatim text in footnotes
$endif$
$if(geometry)$
$if(beamer)$
\geometry{$for(geometry)$$geometry$$sep$,$endfor$}
$else$
\usepackage[$for(geometry)$$geometry$$sep$,$endfor$]{geometry}
$endif$
$endif$
$if(beamer)$
\newif\ifbibliography
$endif$
$if(listings)$
\usepackage{listings}
\newcommand{\passthrough}[1]{#1}
\lstset{defaultdialect=[5.3]Lua}
\lstset{defaultdialect=[x86masm]Assembler}
$endif$
$if(lhs)$
\lstnewenvironment{code}{\lstset{language=Haskell,basicstyle=\small\ttfamily}}{}
$endif$
$if(highlighting-macros)$
$highlighting-macros$
$endif$
$if(tables)$
\usepackage{longtable,booktabs}
$if(beamer)$
\usepackage{caption}
% Make caption package work with longtable
\makeatletter
\def\fnum@table{\tablename~\thetable}
\makeatother
$else$
% Correct order of tables after \paragraph or \subparagraph
\usepackage{etoolbox}
\makeatletter
\patchcmd\longtable{\par}{\if@noskipsec\mbox{}\fi\par}{}{}
\makeatother
% Allow footnotes in longtable head/foot
\IfFileExists{footnotehyper.sty}{\usepackage{footnotehyper}}{\usepackage{footnote}}
\makesavenoteenv{longtable}
$endif$
$endif$
$if(graphics)$
\usepackage{graphicx}
\makeatletter
\def\maxwidth{\ifdim\Gin@nat@width>\linewidth\linewidth\else\Gin@nat@width\fi}
\def\maxheight{\ifdim\Gin@nat@height>\textheight\textheight\else\Gin@nat@height\fi}
\makeatother
% Scale images if necessary, so that they will not overflow the page
% margins by default, and it is still possible to overwrite the defaults
% using explicit options in \includegraphics[width, height, ...]{}
\setkeys{Gin}{width=\maxwidth,height=\maxheight,keepaspectratio}
% Set default figure placement to htbp
\makeatletter
\def\fps@figure{htbp}
\makeatother
$endif$
$if(links-as-notes)$
% Make links footnotes instead of hotlinks:
\DeclareRobustCommand{\href}[2]{#2\footnote{\url{#1}}}
$endif$
$if(strikeout)$
\usepackage[normalem]{ulem}
% Avoid problems with \sout in headers with hyperref
\pdfstringdefDisableCommands{\renewcommand{\sout}{}}
$endif$
\setlength{\emergencystretch}{3em} % prevent overfull lines
\providecommand{\tightlist}{%
\setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}
$if(numbersections)$
\setcounter{secnumdepth}{$if(secnumdepth)$$secnumdepth$$else$5$endif$}
$else$
\setcounter{secnumdepth}{-\maxdimen} % remove section numbering
$endif$
$if(beamer)$
$else$
$if(block-headings)$
% Make \paragraph and \subparagraph free-standing
\ifx\paragraph\undefined\else
\let\oldparagraph\paragraph
\renewcommand{\paragraph}[1]{\oldparagraph{#1}\mbox{}}
\fi
\ifx\subparagraph\undefined\else
\let\oldsubparagraph\subparagraph
\renewcommand{\subparagraph}[1]{\oldsubparagraph{#1}\mbox{}}
\fi
$endif$
$endif$
$if(pagestyle)$
\pagestyle{$pagestyle$}
$endif$
$for(header-includes)$
$header-includes$
$endfor$
$if(lang)$
\ifxetex
% Load polyglossia as late as possible: uses bidi with RTL langages (e.g. Hebrew, Arabic)
\usepackage{polyglossia}
\setmainlanguage[$polyglossia-lang.options$]{$polyglossia-lang.name$}
$for(polyglossia-otherlangs)$
\setotherlanguage[$polyglossia-otherlangs.options$]{$polyglossia-otherlangs.name$}
$endfor$
\else
\usepackage[shorthands=off,$for(babel-otherlangs)$$babel-otherlangs$,$endfor$main=$babel-lang$]{babel}
$if(babel-newcommands)$
$babel-newcommands$
$endif$
\fi
$endif$
$if(dir)$
\ifxetex
% Load bidi as late as possible as it modifies e.g. graphicx
\usepackage{bidi}
\fi
\ifnum 0\ifxetex 1\fi\ifluatex 1\fi=0 % if pdftex
\TeXXeTstate=1
\newcommand{\RL}[1]{\beginR #1\endR}
\newcommand{\LR}[1]{\beginL #1\endL}
\newenvironment{RTL}{\beginR}{\endR}
\newenvironment{LTR}{\beginL}{\endL}
\fi
$endif$
$if(natbib)$
\usepackage[$natbiboptions$]{natbib}
\bibliographystyle{$if(biblio-style)$$biblio-style$$else$plainnat$endif$}
$endif$
$if(biblatex)$
\usepackage[$if(biblio-style)$style=$biblio-style$,$endif$$for(biblatexoptions)$$biblatexoptions$$sep$,$endfor$]{biblatex}
$for(bibliography)$
\addbibresource{$bibliography$}
$endfor$
$endif$
$if(csl-refs)$
\newlength{\cslhangindent}
\setlength{\cslhangindent}{1.5em}
\newenvironment{cslreferences}%
{$if(csl-hanging-indent)$\setlength{\parindent}{0pt}%
\everypar{\setlength{\hangindent}{\cslhangindent}}\ignorespaces$endif$}%
{\par}
$endif$
$if(title)$
\title{$title$$if(thanks)$\thanks{$thanks$}$endif$}
$endif$
$if(subtitle)$
$if(beamer)$
$else$
\usepackage{etoolbox}
\makeatletter
\providecommand{\subtitle}[1]{% add subtitle to \maketitle
\apptocmd{\@title}{\par {\large #1 \par}}{}{}
}
\makeatother
$endif$
\subtitle{$subtitle$}
$endif$
\author{$for(author)$$author$$sep$ \and $endfor$}
\date{$date$}
$if(beamer)$
$if(institute)$
\institute{$for(institute)$$institute$$sep$ \and $endfor$}
$endif$
$if(titlegraphic)$
\titlegraphic{\includegraphics{$titlegraphic$}}
$endif$
$if(logo)$
\logo{\includegraphics{$logo$}}
$endif$
$endif$
\begin{document}
$if(has-frontmatter)$
\frontmatter
$endif$
$if(title)$
$if(beamer)$
\frame{\titlepage}
$else$
\maketitle
$endif$
$if(abstract)$
\begin{abstract}
$abstract$
\end{abstract}
$endif$
$endif$
$for(include-before)$
$include-before$
$endfor$
$if(toc)$
$if(toc-title)$
\renewcommand*\contentsname{$toc-title$}
$endif$
$if(beamer)$
\begin{frame}[allowframebreaks]
$if(toc-title)$
\frametitle{$toc-title$}
$endif$
\tableofcontents[hideallsubsections]
\end{frame}
$else$
{
$if(colorlinks)$
\hypersetup{linkcolor=$if(toccolor)$$toccolor$$else$$endif$}
$endif$
\setcounter{tocdepth}{$toc-depth$}
\tableofcontents
}
$endif$
$endif$
$if(lot)$
\listoftables
$endif$
$if(lof)$
\listoffigures
$endif$
$if(linestretch)$
\setstretch{$linestretch$}
$endif$
$if(has-frontmatter)$
\mainmatter
$endif$
$body$
$if(has-frontmatter)$
\backmatter
$endif$
$if(natbib)$
$if(bibliography)$
$if(biblio-title)$
$if(has-chapters)$
\renewcommand\bibname{$biblio-title$}
$else$
\renewcommand\refname{$biblio-title$}
$endif$
$endif$
$if(beamer)$
\begin{frame}[allowframebreaks]{$biblio-title$}
\bibliographytrue
$endif$
\bibliography{$for(bibliography)$$bibliography$$sep$,$endfor$}
$if(beamer)$
\end{frame}
$endif$
$endif$
$endif$
%% $if(biblatex)$
%% $if(beamer)$
%% \begin{frame}[allowframebreaks]{$biblio-title$}
%% \bibliographytrue
%% \printbibliography[heading=none]
%% \end{frame}
%% $else$
%% \printbibliography$if(biblio-title)$[title=$biblio-title$]$endif$
%% $endif$
$endif$
$for(include-after)$
$include-after$
$endfor$
\end{document}
