The crystal structure of CuBiSeCl2 is most similar to that of MnBiSe2Br, which also crystallizes in the space group Pnma. A structural comparison between the unit cells of CuBiSeCl2 and MnBiSe2Br can be found in the Supporting Information (S9). The structure of MnBiSe2Br consists of layers of MnSe4Br2 octahedra and BiSe5Br3 polyhedra and, like the Cu displacement in CuBiSeCl2, MnBiSe2Br exhibits a deviation in the position of Mn from the centre of the MnSe4Br2 octahedra and towards the Br-Br octahedral edge. Bi occupies split sites in MnBiSe2Br, with the Bi1 site exhibiting an occupancy of 0.97 and the Bi2 site possessing an occupancy of 0.03. In CuBiSeCl2, the Cu is displaced much more significantly from the centre of the octahedra compared to the displacement of Mn observed in MnBiSe2Br. The differences in the cationic displacement magnitude observed in the two structures is partly due to the stoichiometric variation in the local environments, which results in different coordination and bonding.