I am currently looking for a postdoctoral position.
The PhD I did was quite multidisciplinary, and among the fields within there is a field "A" that I would like to investigate further during my postdoc in order to get specialized into it.
However, while I found postdoc opportunities in other fields, it is relatively hard for me to find positions in this field (I think one of the reasons is that my main papers related to this topic are not yet published). A good news is that I have an opportunity in doing a postdoc in this field with someone I collaborated a lot during my PhD and with whom I enjoyed working (it is of course not my advisor, but some permanent researcher from a laboratory of another country).
My issue is that I have heard that it is not good to do a postdoc with someone you already worked with during your PhD. For an academic carreer, people want you to show "independency", and it is from what I understood translated in "you need to work with people you did not work with during your PhD". I wanted to know if it is true (to be honest you could lack total independency working with a completely new person this is why I don't understand this claim). During my PhD I worked on four papers and my two main ones are done in collaboration with this person. Also, what I would do in this postdoc couldn't be considered as being the same job as what I did during my PhD: it could really be seen as a strong specialization in a subfield.
Is it really a bad idea to do a postdoc with someone you already collaborated during your PhD? In the worst case, what if I do a first postdoc with this person and another one with another person? How will this be viewed for my future academic career? The work done in this postdoc will allow me to be specialized in a subfield that was among the fields I work on during my multidisciplinary PhD. In case it wasnt clear: my goal is to find a permanent academic position later on (ideally in France or in neighboring countries).
Additional info: What I know for sure is that doing a postdoc in the same group you did your PhD can be seen as a red flag by recruiters. I know this from various permanent researchers. The context of my question is to ask if it is the same for a collaborator you worked with. Or if it wouldnt be seen as "too close" (and hence, fine).