We report the first experimental determination of the orientation of the main axes of the constant-energy ellipsoids of the secondary valence-band extrema of PbTe. These extrema are generally believed to be located at the $\Sigma$ point of the Brillouin zone. Investigation of the anisotropic behavior of the coefficient of the conductivity of warm holes shows that the main axes of these ellipsoids are parallel to $〈100〉$ and do not coincide with the symmetry direction of the $\Sigma$ point.

• Received 30 June 1975

DOI:https://doi.org/10.1103/PhysRevLett.35.1107