It is worth mentioning however that while the zT is expected to increase with valley degeneracy, intervalley scattering mechanisms (which reduce the benefit of N V ) may become nonnegligible when multiple carrier pockets are present. As this is outside the scope of the present study, we leave the effects of intervalley scattering in compounds with multiple carrier pockets to a future study. Our analysis also holds for materials in which band inversion occurs at a k-point with 3m point group symmetry. Notably, our model explains the dissimilar Fermi surface geometries of Bi 2 Te 3 and Bi 2 Se 3 , where the k-point at which band inversion occurs (Γ) also has 3m point group symmetry. Our analysis suggests that one reason why Bi 2 Te 3 exhibits high valley degeneracy whereas Bi 2 Se 3 exhibits single valley degeneracy is because the bands are sufficiently inverted in Bi 2 Te 3 . Even though band inversion exists in Bi 2 Se 3 , it is not enough to move the band extrema off the Γ point. In general, although the specific Fermi surface geometry depends on complex interactions, there appears to exist a critical degree of inversion, below which the Fermi surface remains single-valleyed.