Notwithstanding what the Internet tells us, the PC-12 is the U-28 rather than UC-28 in US military service. There are apparently two variants, U-28A and U-28B, though I have no idea what the difference is between them.
A UC-28 would be a variant of the C-28, aka the Cessna 404 Titan, a couple of which were operated by the US Navy in the past.