Structure and Properties of Single Crystalline CaMg₂Bi₂, EuMg₂Bi₂, and YbMg₂Bi₂

Single crystals of CaMg₂Bi₂, EuMg₂Bi₂, and YbMg₂Bi₂ were obtained from a Mg–Bi flux cooled to 650 °C. These materials crystallize in the CaAl₂Si₂ structure-type (P3̅m1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg₂Bi₂ displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg₂Bi₂ reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) × 10¹⁹ cm^–3 for CaMg₂Bi₂, 1.7(1) × 10¹⁹ cm^–3 for EuMg₂Bi₂, and 4.6(7) × 10¹⁹ cm^–3 for YbMg₂Bi₂, which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios ρ(300 K)/ρ(10 K) ≤ 1.6 in all cases, indicating significant defect scattering.