Reseach and teaching recommendation letter from the same person

Question

I am applying for a postdoc position.

1. I am wondering if it's acceptable for one of my advisors to write a letter of recommendation for research and teaching? I have been TA for my advisor a couple of times. Does this look good for hiring committee?
2. In mathjobs, I listed the name of my advisor twice (the one who writes research and teaching letters) and 3 other people who will write letters for me (4 people in total and my advisor is counted twice). However, when applying, I see that my advisor is counted once. How to indicate him also as a person who is writing two letters?

Thank you!

Answer 1

No, you should not ask for two different letters from the same person, and I'm surprised your advisor didn't already tell you this. This would be very unusual, and not make your application stand out in a good way. (I have seen thousands of applications on mathjobs, and I don't remember ever seeing this.)

Your advisor should write a letter that focuses on your research, though it's common for that letter to also comment on your teaching. Committees want to see an independent assessment of your teaching (advisors' letters are often biased), but for most research-oriented postdocs, they're not looking for a lot from the teaching letter, just evidence that you'll do a reasonably good job in the classroom.

Some departments have a standard person to write teaching letters for students, so that's one option. Or if you had some sort of teaching mentor/supervisor, or TA'ed for someone else, those are other options. If you're still at a loss, ask your advisor for suggestions.

Answer 2

I think the amount this matters is very position and field dependent, but in general, my gut feeling is that getting recommendations / referee letters from two people looks better than from one.

In my field (Chemistry) I have worked with a few Profs for whom good recommendations (admittedly, research ones) are key and without one you would not get a foot in the door. I have also worked in a position where the "recommendation" requirement was a formal one, used to evaluate whether anyone at all is willing to support you, because - as the head of the committee said: we're judging the quality of the candidate, not of the referee.

My suggestion would be to find someone else involved in the course you helped teach, and approach them for your teaching recommendation. Even in small departments there are often multiple people involved in a single course. I had my senior co-tutor, who was very junior faculty at the time, write one for me!