We apply the proposed material descriptors to computationally search for roomtemperature TE materials among narrow-gap and semimetallic Zintl phases. The search focuses on Zintl phases because they are known to have narrow gaps and in some cases, negative gaps (semimetals). The tiered computational workflow is depicted in Figure . First, we calculate the electronic structures of 650 Zintl phases in the Inorganic Crystal Structure Database (ICSD) with density functional theory (DFT) using the low-cost, semilocal PBE-GGA functional. By analyzing the features of the electronic structure (see Section 5 for details), we identify 44 Zintl phases that are potentially narrow-gap semiconductors or semimetals. Next, we evaluate the material descriptors and estimate the maximum zT at 300 K (using the two-band model, Section 2) of the 44 phases. Since DFT calculations with semilocal functionals tend to unsystematically underestimate the band gaps, we assume a band gap of 0.3 eV and perform a scissor operation to adjust the band gaps. Here, the assumed band gap is simply to aid in materials screening. We also calculated the material descriptors for Mg 3 Bi 2 for validation and benchmarking purposes. Details of the DFT and other calculations are provided in Section 5.