Modify \cite to [Number](Author+Year)

Question

My university want to use a cite style mixture from Harvard and Numeric style. Number I only get [Number (Author+Year)] with my example instead of [ Number ] (Author+Year). So I have some issues with brackets.

\documentclass[a4paper,fontsize=12pt,parskip]{scrbook}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Layout
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
%
\usepackage[labelfont={bf}]{caption}
\usepackage{subcaption}
\usepackage[pdfborder={0 0 0}]{hyperref}
\usepackage[]{geometry}
\renewcommand{\baselinestretch}{1.2}          
\setlength\parindent{0pt}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Seitenränder und Abstände
\geometry{
    textwidth=150mm,
    textheight=220mm,
    top=40mm,
}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Literaturverzeichnis
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage[german=guillemets]{csquotes}
%
\usepackage[backend=biber,style=numeric,maxnames=5,minnames=5,maxcitenames=2,mincitenames=1,datamodel=eprint-hal]{biblatex}
\renewbibmacro*{cite}{%
  \printtext[bibhyperref]{%
      \printtext[hardbrackets]{%
      \printfield{prefixnumber}%
      \printfield{labelnumber}%
      \ifbool{bbx:subentry}
        {\printfield{entrysetcount}}
        {}}
    \printtext[parens]{%
    \printnames{labelname}%
    \setunit{\nameyeardelim}%
    \setunit{\addcomma\space}
    \printfield{year}%
}}}
%
\addbibresource{biblatex-examples.bib}
\begin{document}
ba bla
\cite{springer}
%Literaturverzeichnis
\printbibliography[heading=bibintoc,title=Literaturverzeichnis]
\end{document}

Answer 1

In the code that you are using (probably from Is there a package that allows a citation style of [Author, year] [number]?) the brackets are implicitly added by \cite via its wrapper command. This is not something we want for your application, because we have different types of brackets.

It appears to me that it would be easiest to define a new \cite command so that we get full control over the brackets. The remainder of the approach is similar to Is there a package that allows a citation style of [Author, year] [number]?.

\documentclass[12pt]{article}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[pdfborder={0 0 0}]{hyperref}
\usepackage[german=guillemets]{csquotes}
\usepackage[
  backend=biber,
  style=numeric,
  maxbibnames=5, minbibnames=5,
  maxcitenames=2, mincitenames=1,
]{biblatex}
\newbibmacro*{naycite}{%
  \printtext[bibhyperref]{%
    \printtext[brackets]{%
      \printfield{labelprefix}%
      \printfield{labelnumber}%
      \ifbool{bbx:subentry}
        {\printfield{entrysetcount}}
        {}}
    \setunit{\addspace}%
    \printtext[parens]{%
      \printnames{labelname}%
      \setunit{\printdelim{nameyeardelim}}%
      \printdate}}}
\DeclareCiteCommand{\naycite}
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{naycite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}
\DeclareMultiCiteCommand{\naycites}{\naycite}{\multicitedelim}
\DeclareAutoCiteCommand{nay}{\naycite}{\naycites}
\ExecuteBibliographyOptions{autocite=nay}
\addbibresource{biblatex-examples.bib}
\begin{document}
lorem \autocite{sigfridsson}
lorem \autocite{springer}
\printbibliography[heading=bibintoc,title=Literaturverzeichnis]
\end{document}

If you want bigger brackets around the entire expression you could try something like

\newrobustcmd*{\mkbibbiggerbrackets}[1]{%
  {\large[}#1{\large]}}
\DeclareCiteCommand{\naycite}[\mkbibbiggerbrackets]
  {\usebibmacro{prenote}}
  {\usebibmacro{citeindex}%
   \usebibmacro{naycite}}
  {\multicitedelim}
  {\usebibmacro{postnote}}

Not that I'd recommend it in any shape or form.