The orientation of the main axis of the constant-energy ellipsoids and the mass-anisotropy ratio $\frac{m_l}{m_t}$ of the secondary valence-band extrema of PbTe has been determined experimentally. These extrema are generally believed to be located at the $\Sigma$ point of the Brillouin zone. Investigation of the anisotropy behavior of the coefficient of the conductivity of warm holes and magnetoresistance measurements showed that the main axes of these ellipsoids are parallel to <100> and do not coincide with the symmetry direction of the $\Sigma$ point. The value of the mass-anisotropy ratio for the secondary valence band in PbTe is approximately 10. It has been derived from magnetoresistance experiments.

• Received 28 February 1977

DOI:https://doi.org/10.1103/PhysRevB.16.680