Striker Nick Blackman is United's sixth new addition of the summer - signing for an undisclosed fee from Blackburn.
The 22-year-old had signed a two-year deal with an option for a third year.
The striker, who has had loan spells at Blackpool, Oldham, Motherwell and Aberdeen, is likely to be part of United's squad for the Capital One League Cup tite against Burton Albion on Saturday (3pm kick-off).
He joins Darryl Westlake, John Cofie, Matt Hill, Tony McMahon and Shaun Miller, who have already been recruited.
Reaction to Nick's signing to follow on sufc.co.uk