Uthar's utc file? from a quick search, I found 2 files for Uthar. 1 for the academy (for his academy dialog), and 1 for his dialog in Naga Sadow's tomb.
If you want his academy utc file, you can find it in korr_m35aa_s.rim, called korr35_utharwynn.utc
If you want his Naga Sadow utc file, you can find it in korr_m39aa_s.rim, called, (big surprise) korr39_utharwynn.utc
In those files, you can find his dialog file names, which I bet is what you also want. In the _s.rim files, you can find his dialog files as well. They are titled the same, just with a .dlg extension instead of a .utc