  Different computational scheme for calculating surface integrals in
anisotropic Brillouin zones are compared. The example of the transport
distribution function (plasma frequency) of the thermoelectric Material \BiTe
near the band edges will be discussed. The layered structure of the material
together with the rhombohedral symmetry causes a strong anisotropy of the
transport distribution function for the directions in the basal (in-plane) and
perpendicular to the basal plane (out-of-plane). It is shown that a thorough
reciprocal space integration is necessary to reproduce the
in-plane/out-of-plane anisotropy. A quantitative comparison can be made at the
band edges, where the transport anisotropy is given in terms of the anisotropic
mass tensor.
