Cite only last name instead of full name

Question

In my references I want to show the last name of the author and then the first name:

[GNK17]  Gradstein, Helen et al. “Distributed ledger technology and blockchain”.In: (2017).url:http://hdl.handle.net/10986/29053(visited on09/16/2021)

When I use \citet the output I get is: Gradstein, Helen et al. (2017)

But I want: Gradstein et al. (2017)

This is how I create my references, I put each name in braces.

@article{DLT2,
  title={Distributed ledger technology and blockchain},
  author={{Gradstein, Helen} and {Natarajan, Harish} and {Krause, Solvej}},
  year={2017},
  publisher={World Bank, Washington, DC},
  URL={http://hdl.handle.net/10986/29053},
  urldate={2021-09-16}
}

And this is the configuration:

\usepackage[backend=bibtex,style=alphabetic,citestyle=authoryear,natbib=true,maxnames=2,uniquename=false]{biblatex}

Answer 1

Do not use braces around people's names. This forces a particular reading of the name that does not allow BibTeX (or Biber) to split it into given and family name parts.

You can get the desired name format in the bibliography by redefining name formats instead of forcing them with curly braces.

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[
  backend=bibtex,
  style=alphabetic,
  citestyle=authoryear,
  maxnames=2,
  uniquename=false,
  natbib=true,
]{biblatex}

\DeclareNameAlias{author}{sortname}
\DeclareNameAlias{editor}{sortname}
\DeclareNameAlias{translator}{sortname}

\DeclareNameAlias{sortname}{family-given}

\begin{filecontents}{\jobname.bib}
@techreport{DLT2,
  title       = {Distributed Ledger Technology and Blockchain},
  author      = {Natarajan, Harish and Krause, Solvej and Gradstein, Helen},
  year        = {2017},
  type        = {FinTech Note},
  number      = {1},
  institution = {World Bank},
  location    = {Washington, DC},
  url         = {http://hdl.handle.net/10986/29053},
  urldate     = {2021-09-16},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}

\begin{document}
Lorem \autocite{sigfridsson,DLT2}

\printbibliography
\end{document}

---

The alphabetic labels in the bibliography serve no purpose at all if you cite in author-year format in the text. So I suggest you replace style=alphabetic,citestyle=authoryear, with style=authoryear, for a proper author-year style. In that case you can get rid of a few of the \DeclareNameAliases from before.

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[
  backend=bibtex,
  style=authoryear,
  maxnames=2,
  uniquename=false,
  natbib=true,
]{biblatex}

\DeclareNameAlias{sortname}{family-given}

\begin{filecontents}{\jobname.bib}
@techreport{DLT2,
  title       = {Distributed Ledger Technology and Blockchain},
  author      = {Natarajan, Harish and Krause, Solvej and Gradstein, Helen},
  year        = {2017},
  type        = {FinTech Note},
  number      = {1},
  institution = {World Bank},
  location    = {Washington, DC},
  url         = {http://hdl.handle.net/10986/29053},
  urldate     = {2021-09-16},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\addbibresource{biblatex-examples.bib}

\begin{document}
Lorem \autocite{sigfridsson,DLT2}

\printbibliography
\end{document}

---

Note that I changed your example entry from @article (which is only to be used for papers/articles published in a journal) to @techreport (which is used for working papers and the like). I also used the order of authors shown in http://hdl.handle.net/10986/29053 and in the Acknowledgments section.