The 23-year-old attacking midfielder – the son of ex-USA internationalist John Harkes – has agreed a two-year deal at Tannadice after leaving MLS side DC United.
Harkes joins Aidan Nesbitt (MK Dons), Cammy Smith (St Mirren) and Morgaro Gomis (Sur Club) at the Championship club, who are just three points behind leaders Ross County.
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