We demonstrate the electrical and thermal transport properties of polycrystalline CoPn2 (Pn = As and Sb) between 300 and 900 K. CoAs2 shows semiconducting electrical transport up to 900 K, while CoSb2 exhibits degenerate conduction. Sign inversion of the Seebeck coefficient is observed at ∼310 and ∼400 K for CoAs2 and CoSb2, respectively. Thermal conductivity at 300 K is 11.7 Wm-1K-1 for CoAs2 and 9.4 Wm-1K-1 for CoSb2. The thermoelectric power factor of CoAs2 is ∼10 μWcm-1K-2, although the dimensionless figure of merit is limited to ∼0.1 due to relatively high thermal conductivity. Using electronic structure calculations, the band gap value is calculated to be 0.55 eV for CoAs2 and 0.26 eV for CoSb2.
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