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The superconducting properties and possible nematic superconductivity of the self‐doped BiCh2‐based (Ch: S, Se) superconductor CeOBiS1.7Se0.3 are investigated through measurements of the in‐plane anisotropy of magnetoresistance (MR). Single crystals of CeOBiS1.7Se0.3 are grown using a flux method. The single‐crystal structural analysis reveals that the crystal structure at room temperature is tetragonal (P4/nmm). Bulk superconductivity with a transition temperature of 3.3 K is observed through electrical resistivity and magnetization measurements. Investigation of the anisotropy of the upper critical field suggests relatively low anisotropy in the crystal compared to that of other BiCh2‐based superconductors. In the superconducting states of CeOBiS1.7Se0.3, a twofold symmetric in‐plane anisotropy of MR is observed, which indicates the in‐plane rotational symmetry breaking in the superconducting states of CeOBiS1.7Se0.3.

Zintl compounds containing Sb have been studied extensively because of their promising thermoelectric properties. In this study, we prepared As/P-based Zintl compounds, EuIn2As2-xPx (x = 0 to 2) and SrSn2As2, and examined their potential for use as thermoelectric materials. These compounds show hole carrier concentrations of ~10^19 /cm3 for EuIn2As2-xPx and ~10^21 /cm3 for SrSn2As2 at 300 K. The high carrier concentration of SrSn2As2 is likely owing to self-doping by hole-donating Sn vacancies. The electrical power factor reaches ~1 mW/mK2 at ~600 K for EuIn2As2-xPx with x = 0.1 and 0.2. The lattice thermal conductivity is determined to be 1.6–2.0 W/mK for EuIn2As2 and SrSn2As2, and 2.8 W/mK for EuIn2P2 at 673 K. The dimensionless figure of merit reaches ZT = 0.29 at 773 K for EuIn2As2-xPx with x = 0.2. First-principles calculations show that EuIn2As2 and SrSn2As2 are topologically nontrivial materials with band inversion, while EuIn2P2 is a conventional semiconductor with a bandgap. The present study demonstrates that As/P-based Zintl compounds can also show promising thermoelectric properties, thus expanding the frontier for efficient thermoelectric materials.

Zintl compounds containing Sb have been studied extensively because of their promising thermoelectric properties. In this study, we prepared As/P-based Zintl compounds, EuIn2As2−xPx (x = 0 to 2) and SrSn2As2, and examined their potential for use as thermoelectric materials. These compounds show p-type polarity with Hall carrier concentrations of ~10 19 cm −3 for EuIn2As2−xPx and ~10 21 cm −3 for SrSn2As2 at 300 K. The high carrier concentration of SrSn2As2 is likely owing to self-doping by hole-donating Sn vacancies. The electrical power factor reaches ~1 mW m 1 K 2 at ~600 K for EuIn2As2−xPx with x = 0.1 and 0.2, which is almost twice that of the end-member compounds (x = 0 and 2). The lattice thermal conductivity l is determined to be 1.6-2.0 W m 1 K 1 for EuIn2As2 and SrSn2As2 and 2.8 W m 1 K 1 for EuIn2P2 at 673 K. The dimensionless figure of merit reaches ZT = 0.29 at 773 K for EuIn2As2−xPx with x = 0.2 owing to the optimized carrier concentration and/or electronic structure, as well as a reduced lattice thermal conductivity in the solid solution. First-principles calculations show that EuIn2As2 and SrSn2As2 are topologically nontrivial materials with band inversion, while EuIn2P2 is a conventional semiconductor with a bandgap. The present study demonstrates that As/P-based Zintl compounds can also show promising thermoelectric properties, thus expanding the frontier for efficient thermoelectric materials.

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