It is noteworthy that Sb2Si2Te6 exhibits an energy difference of 0.3 eV between the lowest two conduction band valleys (i.e., ECB1-ECBM) and 0.6 eV between the highest two valence band valleys (i.e., EVBM-EVB1). In contrast, Sc2Si2Te6 features two identical CBM valleys (Σ and Σˊ) and a doubly orbital-degenerate Te-p VBM. Reduced energy differences between adjacent bands near the Fermi level result in increased effective band degeneracy, thus yielding a higher effective DOS in Sc2Si2Te6. As a result of the differing locations of the band extrema in Sb2Si2Te6 (both VBM and CBM at Z) and