Continuing to list as second affiliation an institute where you've never had a paid position This question is similar to other questions of affiliation, but I cannot find anything that quite addresses it. Perhaps this is closest: Adding affiliation due to a 1-month visit during a salary gap
I am the PI on a grant in mathematics. On the grant I have a collaborator and postdoc employed at 100% capacity (1 FTE). We are about to have a paper published. In addition to his current affiliation, University A, he wants to list University B at which he did his last postdoc, which I think is fine as much of the work on the paper was carried out there.
In addition, he wants to list a third affiliation, University C. He has never had a paid position at University C. It seems that someone at University C said it would be okay to use this affiliation during a period of time when he was unemployed but looking for another postdoc. None of the work of the current paper was done during this time of unemployment. Indeed, he plans to keep using this affiliation in the future. As far as I know, he has no collaborations with any researchers there, nor has he lived in the city where the university is located during this time of unemployment. I cannot find any online reference to his being at that university, other than those references he has created himself (eg. I find papers of his, or his CV or personal website, but nothing from the university itself).
Is using this affiliation ethical?
I understand that one should generally leave it up to their collaborators to decide their affiliations. However, in this case, he is employed on my grant at 100% capacity and I am worried the granting agency will not be happy that he is also apparently employed at the same time at another university in another country.
I have suggested he put University C in the acknowledgments section, but he is not willing to accept this compromise.
It’s dishonest (and therefore unethical in almost all normal circumstances) to represent yourself as something you’re not. That’s what your grant employee wants to do by listing his affiliation as a place where he doesn’t hold an official title (and it’s irrelevant whether “someone said it’s okay” unless perhaps that someone is a dean or a similar high-ranking person who has the authority to give people official titles; it’s also not strictly speaking relevant whether he had a “paid position” or not - some official titles are unpaid).
As for what to do, I agree with your reasoning that this is your responsibility since he is paid with your grant funds. It’s perfectly appropriate for you to say that he cannot write this dishonest affiliation in any paper that is funded by your grant. If he does not accept this, you should check with your institution what enforcement or disciplinary measures can be taken in connection with this type of employee insubordination. It may also be worth trying to talk to him informally (perhaps in the presence of a “neutral” senior colleague) and see if you can understand the motive for this behavior; possibly it’s based on some misconception on the part of the employee, and you may be able to convince him that there’s nothing to be gained, and much to be lost, from this type of dishonest behavior.