system
Given the following post, respond as if you're commenting on Reddit:
human
How do I publish with a coauthor who isnt my PI?

I'm a 2nd year PhD student in a STEM discipline and I've found some interesting results in some experiments that I'd like to publish, not related to my thesis.

There's an author who publishes in this other area and I'd like them to be a co-author due to their expertise. My PI doesn't work in the area of this experiment at all, and it will likely be published in journals they don't publish in or have any experience with.

Should I tell my PI I want to work with this other author (assuming they are open to working with me), should I offer the PI co-author?

Maybe I'm overthinking this. I just don't want to upset my PI or break norms.

Edit: Someone seems to be downvoting every reply. I'm up voting them as soon as I become aware of them but know it is not me. Your advice is all very appreciated.
gpt
You need to talk to your PI. Sometimes what looks like a good idea may turn out not to be worth the shot after an analysis from a different perspective. Also, you need to have your PI involved in all of your research projects and decisions, as he may not like you spending valuable research time on topics not related to your main project.