[en] Structural and transport properties of Cs₈Cd₄SN₄2 are reported. Cs₈Cd₄Sn₄2 has a thermal conductivity that is unusually low for a cystalline solid (1 W m^-1 K^-1 at room temperature). This low lattice thermal conductivity is associated with the rattling of cesium in the tetrakaidecahedral cavities, as indicated by the large atomic displacement parameters of Cs in the tetrakaidecahedra. Resonant X-ray powder diffraction measuerments indicate that all of the cadmium is located on one of three inequivalent framework sites. There is no evidence for any framework vacancies in the material