This question already has an answer here:
I am currently a PhD at a decent university in Math and applying for a part time grad student job in a Fintech company in one of the major centers for finance. I applied for the job by responding to an e-mail and now they asked me to do an onsite interview. The entire application process was informal since they always addressed me by my first name and now I wonder what I should wear. I just wonder whether wearing a suit might be weird in this case?