“…Note that Cu 4 SnS 4 ,t etrahedrite,a nd talnakhite,d espite the aforementioned differences,e xhibit extremely low thermal conductivity. [59,61,62,64,65] Group Ealso includes n-type compounds (Cu/M < 1) such as thiospinel Cu 2 CoTi 3 S 8 (Fd3 ¯m, a = 9.885 , V = 966.0 3 ), [66] which contains CuS 4 tetrahedra and (Ti,Co)S 6 octahedra, and the synthetic phase Cu 4 Sn 7 S 16 (R3 ¯m, a = 7.372 , c = 36.010 , V = 1694.8 3 ), [67] which contains CuS 6 and SnS 6 octahedra as well as CuS 4 tetrahedra, some of them leaning strongly toward aC uS 3 trigonal-planar coordination (Figure 6c). Essentially,t he crystal structure of Cu 4 Sn 7 S 16 can be described as ad efect (thio)spinel AB 2 X 4 (unit cell parameter a' % 10.…”