I'd always wear a shirt and tie and a suit to an interview.
Shows a basic respect even if it's not obligatory.
i would go in a suit, failing that a smart pair of pants, shirt & tie
I did this too and now i am working there and the dress code is casual basically what ever you like, no harm in being smartly dressed.
The thing is if you dress in a suit and all the other applicants dress casually then it's a reason for you to stand out in the interviewers mind. Every little advantage counts.