ELECTRONIC TRANSPORT IN LIGHTLY DOPED COSB3

We report resistivity, Hall coefficient, and Seebeck coefficient measurements on a very lightly doped (1/R(H)e = 7.0 X 10(16) holes/cm(3)) single crystal of CoSb3. The low-temperature resistivity is semiconducting, with a gap E(g) = 580 K ( approximate to 50 meV). At high temperatures another energy scale is apparent, with a characteristic energy E(g) = 3650 K ( approximate to 0.31 eV). The presence of two energies is consistent with a recent band-structure calculation performed by Singh and Pickett. The Hall coefficient is large and positive, as expected for a lightly doped p-type semiconductor. Below 200 K, the Hall mobility R(H) sigma varies as T-3/2 indicating that ionized impurity scattering is the dominant scattering mechanism. The Hall mobility peaks at 250 K at value of 1940 cm(2) V-1 sec(-1). The Seebeck coefficient is small at low temperature, and increases smoothly until it attains a value of 225 mu V/K at 300 K; its temperature dependence is also consistent with ionized impurity scattering. A detailed structural refinement on our crystals gives a lattice parameter of 9.03573(3) Angstrom, with evidence for little or no site disorder.