Only use first of double surnames in biblabel with biblatex

I have the following bibliography setup

documentclass[ngerman]{article}

usepackage{babel}
usepackage{csquotes}
usepackage{filecontents}

usepackage[backend=biber,
            style=ieee-alphabetic,
            maxnames=99,
            maxcitenames=2,
            minalphanames=1, maxalphanames=1,
            giveninits=true,
            useprefix=false,
            doi=false, isbn=false, url=false,
            backref=false,
            dashed=false,
            ]{biblatex}
renewcommand*{labelalphaothers}{}


DeclareLabelalphaTemplate{
  labelelement{
    field[final]{shorthand}
    field{label}
    field{labelname}
  }
  labelelement{
    field{year}
  }
}

begin{filecontents}{jobname.bib}
@article{Garcia1984,
  author  = {García Lopéz, Frank and Orwell, George},
  title   = {1984},
  year    = {1948},
  journal = {Books About Big Brothers},
  volume  = {5},
  number  = {42},
  pages   = {100--111},
}
end{filecontents}
addbibresource{jobname.bib}
begin{document}

cite{Garcia1984}.
printbibliography
end{document}

With the following output:

Do you see any possibility to only show the first of the two surnames of the first author in the biblabel, so it is [García1984]? I could live with only the second name, if that would be easier, but knowing Spanish/Latin American people and how they use their names, I think the former is the preferable choice.

In the bibliography entry the name should remain as it is, so F. G. Lopéz or F. García L. are no options.

Thanks in advance!

documentclass[ngerman]{article}
usepackage{babel}
usepackage{csquotes}

usepackage[
  backend=biber,
  style=ieee-alphabetic,
  maxnames=99, maxcitenames=2, minalphanames=1, maxalphanames=1,
  giveninits=true, useprefix=false,
  doi=false, isbn=false, url=false,
  dashed=false,
]{biblatex}

renewcommand*{labelalphaothers}{}

DeclareLabelalphaTemplate{
  labelelement{
    field[final]{shorthand}
    field{label}
    field{labelname}
  }
  labelelement{
    field{year}
  }
}

begin{filecontents}{jobname.bib}
@article{Garcia1984,
  author       = {García Lopéz, Frank and Orwell, George},
  shortauthor  = {García, Frank and Orwell, George},
  title        = {1984},
  year         = {1948},
  journal      = {Books About Big Brothers},
  volume       = {5},
  number       = {42},
  pages        = {100--111},
}
end{filecontents}
addbibresource{jobname.bib}
begin{document}

cite{Garcia1984}.
printbibliography
end{document}

documentclass[ngerman]{article}

usepackage{babel}
usepackage{csquotes}
usepackage{filecontents}

usepackage[backend=biber,
            style=ieee-alphabetic,
            maxnames=99,
            maxcitenames=2,
            minalphanames=1, maxalphanames=1,
            giveninits=true,
            useprefix=false,
            doi=false, isbn=false, url=false,
            backref=false,
            dashed=false,
            ]{biblatex}
renewcommand*{labelalphaothers}{}

letMYSEPrelax
DeclareLabelalphaTemplate{
  labelelement{
    field[final]{shorthand}
    field{label}
    field{labelname}
  }
  labelelement{literal{MYSEP}} % <<=======
  labelelement{
    field{year}
  }
}

DeclareFieldFormat{labelalpha}{expandafterextractfirsta#1MYSEP}

defextractfirsta#1MYSEP#2MYSEP{extractfirstb#1 MYSEP{#2}}
defextractfirstb#1 #2MYSEP#3{#1#3}

begin{filecontents}{jobname.bib}
@article{Garcia1984,
  author  = {García Lopéz, Frank and Orwell, George},
  title   = {1984},
  year    = {1948},
  journal = {Books About Big Brothers},
  volume  = {5},
  number  = {42},
  pages   = {100--111},
}
end{filecontents}
addbibresource{jobname.bib}
begin{document}

cite{Garcia1984}.
printbibliography
end{document}