What are the legal recourses for not forfilling my contract with my employer?

I signed a contract with my employer that I would stay employed for a term of two years for $5,000 in education expenses. I served one year and resigned. What are the legal recourses my employer can take if I dont pay the $5,000? Also since I worked one of the two years shouldn't the repayment be $2,500 since I uphelp half of the contract?