Four new actinide chalcogenides-narnely, Ba2Cu4USe6, Ba2Cu2ThSe5, Ba2Cu2USe5, and Sr2Cu2US5-were synthesized via solid-state methods at 1173 K. Single-crystal X-ray diffraction studies show that Ba2Cu4USe6 crystallizes in a new structure type in space group C-2h(5)-P2(1)/c of the monoclinic system, whereas the three other compounds are isostructural and adopt the Ba2Cu2US5 structure type in space group C-2h(3)-C2/m, also of the monoclinic system. These Ak/Cu/An/Q structures (Ak = alkaline-earth metal; An = actinide; Q = chalcogen) have no short Q-Q interactions and, hence, are charge-balanced with Ak(2+), Cu1+, and Q(2-). Crystal structures of all these compounds are two-dimensional and feature layers that are separated by Ba2+ cations. The compositions of these layers differ. In the structure of Ba2Cu4USe6, the (2)(infinity)[Cu4USe64-] layers comprising USe6 octahedra and CuSe4 tetrahedra stack perpendicular to the a-axis. These (2)(infinity)[Cu4USe64-] layers show short Cu-Cu interactions. In the three isostructural Ak(2)Cu(2)AnQ(5) compounds, An% octahedra and CuQ(4). tetrahedra are connected along the c-axis in the sequence "...oct tet tet oct tet tet..." to form the (2)(infinity)[Cu(2)AnQ(5)(4-)] layers. Resistivity, optical, and DFT calculations show semiconducting behavior for these compounds.