The compound K2Cu3US5 was obtained by the reaction of K2S, UCl4, CuCl, and S at 973 K. K2Cu3US5 crystallizes in a new structure type in space group Cmcm of the orthorhombic system in a cell of dimensions a = 3,9374(6) angstrom, b = 13.813(2) angstrom, c = 17.500(3) angstrom, and V = 951.8(2) angstrom(3) at 153 K. The structure comprise (2)(infinity)[UCu3S52-] slabs separated by K+ cations. The slabs are built from CuS4 tetrahedra and US6 octahedra. Their connectivity differs from other known octahedral/tetrahedral packing patterns. In the temperature range 130-300 K the compound exhibits Curie-Weiss magnetic behavior with u(eff) = 2.45(8) u(B). This result together with both the bond distances and bond valence calculations and the absence of a Cu2+ ESR signal support the formulation of the above compound as K2+Cu3+ U5+S52-.