RMarkdown placement of in_header code and package imports (citation)

[DavidJesse]

Hi,

I am writing a seminar paper for a course at my university using R Markdown.
For citation I use biblatex and the authoryear-icomp citation style.
The (shortened) YAML header of my .Rmd file looks like this:

output:
  bookdown::pdf_document2:
    includes:
      in_header: "tex/preamble.tex"
      before_body: "tex/before_body.tex"
    citation_package: biblatex
    toc: false
    keep_tex: true
bibliography: ["bib/references.bib", "bib/packages.bib"]
biblio-style: authoryear-icomp
documentclass: scrartcl

I would like to increase the space between the single entries in the bibliography, for which I have found possible solutions here.
The issue is that I cannot simply paste the code in the preamble.tex file because of the way RMarkdown or Pandoc create the .tex file.

The following is a snippet from the resulting .tex file:

% --- other stuff --- %
\newcommand{\iid}{\overset{\text{i.i.d.}}{\sim}}
\newcommand{\ind}{\overset{\text{ind.}}{\sim}}
% preamble.tex ends here


\usepackage{booktabs}
\usepackage{longtable}
\usepackage{array}
\usepackage{multirow}
\usepackage{wrapfig}
\usepackage{float}
\usepackage{colortbl}
\usepackage{pdflscape}
\usepackage{tabu}
\usepackage{threeparttable}
\usepackage{threeparttablex}
\usepackage[normalem]{ulem}
\usepackage{makecell}
\usepackage{xcolor}
\ifLuaTeX
  \usepackage{selnolig}  % disable illegal ligatures
\fi
\usepackage[style=authoryear-icomp,backend=biber,maxbibnames=999,maxcitenames=2,uniquelist=false,dashed=false,isbn=false,doi=false,eprint=false]{biblatex}
\addbibresource{bib/references.bib}
\addbibresource{bib/packages.bib}
\IfFileExists{bookmark.sty}{\usepackage{bookmark}}{\usepackage{hyperref}}
\IfFileExists{xurl.sty}{\usepackage{xurl}}{} % add URL line breaks if available
\urlstyle{same} % disable monospaced font for URLs
\hypersetup{
  hidelinks,
  pdfcreator={LaTeX via pandoc}}

\author{}
\date{\vspace{-2.5em}}

\begin{document}

Thus, if I added e.g. \setlength\bibitemsep{1.5\itemsep} to preamble.tex, this line of code would be added before the import of the biblatex package.
But the command needs to be placed after the import and before \begin{document}.

Does anyone have an idea of how to deal with this problem?

Cheers,
David