In this work, we investigate the effects on band degeneracy and thermoelectric performance by modifying the conduction band orbital character in this crystal family, shifting from a Sb-p derived CBM in Sb2Si2Te6 to a Sc-d CBM in Sc2Si2Te6. Sc2Si2Te6 shares an identical stacking fault pattern with Sb2Si2Te6, and crystallizes in the same rhombohedral symmetry (space group R 3 ̅ ) with a single distinct crystallographic position each for Sc, Si and Te as revealed experimentally by high-resolution transmission electron microscopy and diffraction patterns. We systematically investigated the thermal and electrical transport properties in layered Sb2Si2Te6 and Sc2Si2Te6 by solving the Boltzmann transport equation based on first-principles calculations, revealing a significant enhancement of band degeneracy and, consequently, the Seebeck coefficient in Sc2Si2Te6 compared to Sb2Si2Te6. We predict n-type Sc2Si2Te6 to achieve an optimal ZT of 3.51 at 1000 K, surpassing the maximum ZT of 2.76 obtained for p-type Sb2Si2Te6 by 27 %. These findings demonstrate that Sc2Si2Te6 presents a competitive alternative to Sb2Si2Te6, highlighting the validity of band degeneracy engineering in optimizing the PF and thermoelectric performance.