The dependence of the Nernst-Ettingshausen longitudinal effect on the direction of the magnetic field for the case of semimetals is studied theoretically and experimentally. A quite unique correspondence is found between the anisotropy of the effect and the band structure near the Fermi level. It is shown that the commutation effect which determines the dependence of the magneto-thermo-e.m.f. magnitude on the direction of the induction vector, permits to judge about the number and localization of band extrema in the k-space. This is an effective way for studying band structures of bismuth and its alloys a t high temperatures. The results of CE studies in bismuth and its alloys art 100 O K are given below. Theory of Thermomagnetic EffectsThe expression for the electric current density J is given as follows :where oi,(B) is the generalized electroconductivity tensor, E, the electric field, 0, T the temperature gradient.The tensor Pir(B) is determined by the correlation