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Transport, Thermal, and Magnetic Properties of the Narrow-Gap Semiconductor CrSb2

Resistivity, Hall effect, Seebeck coefficient, thermal conductivity, heat capacity, and magnetic susceptibility data are reported for CrSb2 single crystals. In spite of some unusual features in electrical transport and Hall measurements below 100 K, only one phase transition is found in the temperature range from 2 to 750 K corresponding to long-range antiferromagnetic order below T_N ~ 273 K. Many of the low temperature properties can be explained by the thermal depopulation of carriers from the conduction band into a low mobility band located approximately 16 meV below the conduction band edge, as deduced from the Hall effect data. In analogy with what occurs in Ge, the low mobility band is likely an impurity band. The Seebeck coefficient, S, is large and negative for temperatures from 2 to 300 K ranging from ~ -70\muV/K at 300 K to -4500\muV/K at 18 K. A large maximum in |S| at 18 K is likely due to phonon drag with the abrupt drop in |S| below 18 K due to the thermal depopulation of the high mobility conduction band. The large thermal conductivity between 10 and 20 K (~350 W/m/K) is consistent with this interpretation, as are detailed calculations of the Seebeck coefficient made using the complete calculated electronic structure. These data are compared to data reported for FeSb2, which crystallizes in the same marcasite structure, and FeSi, another unusual narrow-gap semiconductor.