Interestingly, the synergy between the electrical and thermal transport with n-type doping is also predicted for the Pnma Sn chalcogenides (Table , ESI † ). We predict ZT max of 2.91 and 4.32 for SnS and SnSe, respectively, along the layered b axes, which are 60% and 80% larger than the averaged values of 1.78 and 2.39. (This may be compared with the p-type ZT max of 1.56 and 2.29 along the c directions, which are both ∼ 10% larger than the average values of 1.39 and 2.07.) Given that successful n-type doping of both SnS and SnSe has been demonstrated, and at comparable n to what we predict is needed, this is also a potentially significant finding.