Using the proposed material descriptors, we assess the TE performances of a set of narrow-gap and semimetallic Zintl phases. In agreement with experiments, we correctly re-identify Mg 3 Bi 2 as a high-performing TE material for room-temperature applications. Mg 3 Bi 2 showcases the importance of the asymmetry parameter; despite being a semimetal, a large R ensures high room-temperature TE performance. From our search, we find four Zintl phases, including SrSb 2 , Zn 3 As 2 , NaZnSb, and NaCdSb, to exhibit relatively high room-temperature TE performance.