Shared first authors in bibliography

Question

In my field it is common to have shared first authorship for authors who “contributed equally to the work” (as shared first authorship is usually defined). The “proper” way of citing publications with shared first authors is to mention all first authors (not just the first first one¹).

Now, normally the citation style for authordate-like formats is along the lines of:

Doe, Jane et al. (1995), “Title”. In: Journal

Whereby the subsequent authors are elided². However, with shared first authors, the citation should look like this:

Jane Doe, Fred Foo et al. (1995), “Title”. In: Journal

I have two (related) questions concerning this:

1. How do I accomplish this citation style in LaTeX using BibLaTeX?
2. How do I even mark shared first authors in the source *.bib file?

The second question is a corollary of the first, since it is my understanding that in a “normal” *.bib file the author field is simply an ordered list, with no means of indicating contribution.

I’m particularly interested in how to accomplish this for biblatex’ authoryear style; however, I’m also interested in a more general solution with full author lists (in which joint first authors could e.g. be marked by an asterisk).

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¹ And this is actually quite important, although disappointingly few publications get it right, because if not done, it skews authorship for the purpose of text mining, and unfairly withholds the equal contributions of the co-first authors.

² Unless there are very few (e.g. < 3), in which case it’s common to cite them all.

Answer 1

I'm not sure there is a 'technical' answer there, at least not with .bib files. The BibTeX format is easy to use and edit but doesn't allow adding XML-like 'meta-data' to authors. Any approach to adding additional markup will end up with repetition

authors  = {A. N. Other and B. Secondauthor and ...
nameauthors =  {A. N. Other and B. Secondauthor}

or need data that will not be transferable between styles

authors  = {A. N. Other* and B. Secondauthor* and ...

Moreover, saying that multiple authors 'should be given for equal credit' is not really what citations are for: they are to allow readers to unambiguously identify references. In areas that use author-date citations, the number of authors given is typically the minimum number to achieve that and typically the most 'important' author(s) are given at the start of the list as a result. However, that's not guaranteed. For example, in my subject area the corresponding (lead) author is commonly (though not exclusively) given last. As such, automated selection of author names is not appropriate and if I want to refer to a group leader I do it by hand

BigName and co-workers have reported~\cite{BigName2015} ...

(My subject area uses numerical citations so the above would have a number not some random first author surname as part of the citation.)

These subtleties are I think only realistically addressed by writing such information by hand in the manuscript.