I have completed experimental research on a novel topic. I was the instigator of the direction of the research and the one to find the results. Then, theoretical work was performed to support my experiments. While the theory confirmed all my work, there was nothing original or new in the theoretical support. I wrote the paper and drafted the manuscript.
The group supervisor wants the theory paper to have the theory researcher as first author. The group leader's arguments is that "there will be two papers, so share the first authorship".
I think this is unfair. Why should I have to share my work just because there will be two papers out of it?!
I am asking for guidance on this. In particular as scientific supervisors, is it fair to put the main researcher as an "et al", just because someone else in the group has not got a paper?