Bismuth telluride (Bi2Te3) is a narrow band gap semiconductor, which is well known as one of the best thermoelectric materials. Recently, this material has been discovered as a new type of quantum matter, a 3D topological insulator (TI). [1] Due to their many remarkable properties [2], topological insulators are now become one of the most actively researched subjects in condensed matter physics. We present here a study of electrical properties of Bi0.5Sb1.5Te3 microwires with different diameters (d=10 – 20 μm). Cylindrical Bi0.5Sb1.5Te3 crystals with glass coating were prepared by the liquid phase casting in a glass capillary. The X-ray studies have shown that the microwire core is in general polycrystal consisting of big disoriented single crystal blocks of approximate size 10- 15 μm. Fig.1. SdH oscillations in dR/dB measured at 4.2 K and 2.1 K for sample Bi0.5Sb1.5Te3, D=30 μm, d=16.8 μm. (a) and (b) show dR/dB vs 1/B after subtracting a smooth background for transverse and longitudinal magnetoresistance respectively; (c) Landau-level fan diagrams for SdH oscillations. Shubnikov de Haas (SdH) oscillations with equal periods ΔB=0.038 T-1 both in longitudinal and transverse magnetic fields for carriers with mc= 0.15m0 in Bi0.5Sb1.5Te3 microwire with d=16.8 μm were observed (see Fig. 1) [3]. Since the sample is polycrystalline, it is possible to conclude that these oscillations could arise from the topological surface states. Assuming that surface electrons are Dirac type, we have obtained the position of the surface Fermi level measured from the Dirac point EF=40 meV, the mean-free path on the surface lS=46 nm and the surface mobility μS≈2500 cm2V-1s-1. Unfortunately, in our rather thick wires the surface conductivity does not play a main role. In order to achieve noticeable effect of increasing thermoelectric efficiency ZT, which was predicted theoretically, it is necessary to investigate thinner samples.