These modem files are huge (50Mb+) compared to the S2 modems (8Mb+)
I've never flashed a modem through Odin before. I assume the .md5 file must be loaded into the PDA section?
Be warned however....Its a slight worry flashing modems on the S4, as a CWM flash is not possible (as yet). This means if things go wrong, the only way back is an Odin flash of the original ROM as modems, of course, do not get backed up in a CWM backup.