Go for a suit. You don't know what the other short-listed people will be wearing, and you definitely do not want to feel under-dressed for this occasion. If you turn out to be overdressed it is not that bad. It shows you've put in too much effort, but the people making the selection won't take this the bad way. Not a black one though, maybe something gray with a light blue shirt. Black shoes, don't go for experiments there. If you are in two minds about a tie, take one with you and see what the other people are like, see how you feel and take it from there. I got my lecturing job in a gray suit, and missed one interviewed in the same one, so can't really say it was the suit. But make sure it is one you feel very comfortable with, and the same is true for the SHOES, don't wear brand new ones, they may kill you on the day.
All the best