[Tex/LaTex] Square brackets with BibLatex in text and bibliography

Question

I have read many related posts regarding the issue of having squared brackets with biblatex. Unfortunately, none have made me fully understand how to compute the squared brackets. I know that biblatex is not compatible with natbib, so that was not an option.

This is what it looks like now in the text:

This is what it looks like in the bibliography:

Disered output: I want to have squared brackets instead of the rounded brackets. It seems very simple, but after many frustrating hours I can't figure it out.

This is what it looks in code:

\usepackage[style=numeric, backend=biber]{biblatex} % Adjust bibliography style
\addbibresource{bibliography.bib} % BibTeX bibliography file
\DeclareFieldFormat{labelnumber}{\RN{#1}}

---

The MWE.tex file:

%----------------------------------------------------------------------------------------
%   DOCUMENTCLASS
%----------------------------------------------------------------------------------------

\documentclass[11pt,a4paper,fleqn,twoside]{book} % Default font size and left-justified equations

%----------------------------------------------------------------------------------------
%   FONTS
%----------------------------------------------------------------------------------------
% itemize with dash
\def\labelitemi{--}

\usepackage{avant} % Use the Avantgarde font

%
\renewcommand{\familydefault}{\sfdefault} % Makes changes in the text font

\usepackage{microtype} % Slightly tweak font spacing for aesthetics
\usepackage[utf8]{inputenc} % Required for including letters with accents
\usepackage[T1]{fontenc} % Use 8-bit encoding that has 256 glyphs


%----------------------------------------------------------------------------------------
%   BIBLIOGRAPHY
%----------------------------------------------------------------------------------------

\usepackage{csquotes}
\usepackage[style=numeric, backend=biber]{biblatex} % Adjust bibliography style
\addbibresource{bibliography.bib} % BibTeX bibliography file
\DeclareFieldFormat{labelnumber}{\RN{#1}}
\defbibheading{bibempty}{}


%----------------------------------------------------------------------------------------
%   START DOCUMENT
%----------------------------------------------------------------------------------------

\begin{document}


%----------------------------------------------------------------------------------------
%   PART II
%----------------------------------------------------------------------------------------

Value-based health care is a health care delivery model that aims to achieve high value for patients, with value defined as health outcomes achieved per dollar spent \cite{porter2010value}.


%----------------------------------------------------------------------------------------
%   BIBLIOGRAPHY
%----------------------------------------------------------------------------------------


\printbibliography


%----------------------------------------------------------------------------------------
%   END DOCUMENT
%----------------------------------------------------------------------------------------

\end{document}

The bibliography.bib file:

@article{porter2010value,
    title={What is value in health care?},
    author={Porter, Michael E},
    journal={New England Journal of Medicine},
    volume={363},
    number={26},
    pages={2477--2481},
    year={2010},
    publisher={Mass Medical Soc}
}

Answer 1

As it turns out what you get in the MWE are square brackets, but avant's square brackets are a bit round at the ends. You can, however, still see a small difference between round brackets and square brackets – at least when you see them side by side.

Here is a solution to let biblatex use the square brackets from Latin Modern Sans. Note that this only changes square brackets under biblatex's control and only those that are properly typeset with \mkbibbrackets and friends. If you are looking for a solution that also replaces the characters [ and ] whenever you type them in, I suggest you ask a new question about that (since it has nothing to do with biblatex at all).

\documentclass[british]{article}

\usepackage{avant}
\renewcommand{\familydefault}{\sfdefault}

\usepackage{microtype}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\usepackage{babel}
\usepackage{csquotes}

\usepackage[style=numeric, backend=biber]{biblatex}

\newcommand*{\sqqbrackleft}{{\usefont{T1}{lmss}{m}{n}\symbol{91}}}
\newcommand*{\sqqbrackright}{{\usefont{T1}{lmss}{m}{n}\symbol{93}}}

\makeatletter
\renewcommand*{\bibleftbracket}{\blx@postpunct\sqqbrackleft}
\renewcommand*{\bibrightbracket}{\blx@postpunct\sqqbrackright\midsentence}
\makeatother

\addbibresource{biblatex-examples.bib}

\begin{document}
[square] (round)

\sqqbrackleft square\sqqbrackright

\cite{sigfridsson}
\printbibliography
\end{document}