We have measured the electrical-transport and magnetic properties of several intermetallic compounds UTSn and UTSb, where T is a transition metal. The electrical resistivity is up to three orders of magnitude larger than usually found for U-based compounds. This is ascribed to the occurrence of a spin polarized energy gap related to the MgAgAs-type crystal structure. For UNiSn at least one spin band closes at low temperature, resulting in half-metallic behavior. Interestingly, the magnetic properties exhibit Kondo-lattice character and weak-moment ordering.