Finally, our predicted ZT for GeS and GeSe are again generally a good match to previous experimental and theoretical studies. In particular, measurements on Ag 0.01 Ge 0.79 Sn 0.2 Se reported a ZT of 0.2 at T = 700 K and n ≈ 10 18 cm -3 , 47 and we obtain the same figure of merit with a similar n = 2 × 10 18 cm -3 . The authors also predicted a significant enhancement to ZT = 0.6 at a larger n ≈ 5 × 10 19 cm -3 , which is consistent with our predicted ZT = 0.87 with n = 4 × 10 19 cm -3 . Previous theoretical studies have also predicted superior TE performance for n-type doping as found in the present study. We note, however, that our predictions show considerably quantitative differences to some previous calculations. For example, the study on Pnma GeS in Ref. predicted a ∼ 2.5× larger κ latt and 50% smaller ZT at 700 K than the present calculations, while Ref. predicted a 5× larger σ , smaller κ el , and 2-4× larger ZT . However, there are considerable technical differences to the present calculations, and the good reproduction of the experimental electrical and thermal properties in this work, and also in our previous study on SnS and SnSe using the same approach, give us confidence in our predictions.