How to reduce line spacing in single-paragraph biblatex bibliography with a small font size

Question

I'm trying to create a compressed, single-paragraph bibliography using biblatex, like in this answer. I'd also like to make the font quite a bit smaller than the main font size of the document. I'm doing this by setting \bibfont; however, this produces something that looks like double spacing, but I only want single spacing. I thought that

\renewcommand*{\bibfont}{\fontsize{5pt}{7pt}\selectfont}

would take care of this because \fontsize is supposed to also set the \baselineskip value. Does anyone know why I have such big line spacing in the bibliography, and how can I reduce this spacing to something that just looks like normal single spacing?

\begin{filecontents*}{\jobname.bib}
@article{a1,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201--204},
  year = {1999},
}
@article{a2,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201--204},
  year = {2000},
}
@article{a3,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201--204},
  year = {2001},
}
@article{a4,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201--204},
  year = {2002},
}
@article{a5,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201--204},
  year = {2003},
}
\end{filecontents*}
\documentclass{article}

\usepackage[american]{babel}

\usepackage{csquotes}

\usepackage[backend=biber,
  style=authoryear-comp,
  maxcitenames=2,
  maxnames=1,
  minnames=1,
  firstinits=true]{biblatex}

\addbibresource{\jobname.bib}

\renewcommand*{\bibfont}{\fontsize{5pt}{7pt}\selectfont}

\defbibenvironment{bibliography}
  {}
  {}
  {\addspace}

\begin{document}

\nocite{*}
\printbibliography

\end{document}

Answer 1

The issue is that, if horizontal mode is not ended in the bibliography environment, then the value of \baselineskip reverts to what it is elsewhere in the document. This is discussed in this answer to Reduce line spacing when using smaller font size in an environment.

You can end the paragraph (i.e., end horizontal mode and force the material to be broken into lines) by putting \endgraf into the <end code> part of the \defbibenvironment command:

\defbibenvironment{bibliography}
  {}
  {\endgraf}
  {\addspace}

You have to use \endgraf here instead of \par, otherwise you'll get an error (see When is it better to use \par than \endgraf? for some discussion of the differences between \par and \endgraf).

Here is the full MWE:

\begin{filecontents*}{\jobname.bib}
@article{a1,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201-204},
  year = {1999},
}
@article{a2,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201-204},
  year = {2000},
}
@article{a3,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201-204},
  year = {2001},
}
@article{a4,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201-204},
  year = {2002},
}
@article{a5,
  author = {Smith, Jane},
  journal = {Nature},
  volume = {7},
  pages = {201-204},
  year = {2003},
}
\end{filecontents*}
\documentclass{article}

\usepackage[american]{babel}

\usepackage{csquotes}

\usepackage[backend=biber,
  style=authoryear-comp,
  maxcitenames=2,
  maxnames=1,
  minnames=1,
  firstinits=true]{biblatex}

\addbibresource{\jobname.bib}

\renewcommand*{\bibfont}{\fontsize{5pt}{7pt}\selectfont}

\defbibenvironment{bibliography}
  {}
  {\endgraf}
  {\addspace}

\begin{document}

\nocite{*}
\printbibliography

\end{document}

And here is the resulting output with something that looks like single line spacing: