The study of the electronic properties of ultrathin films of pure bismuth and bismuth-antimony alloys is of interest, since an increase in conductivity with decreasing sample thickness was found. This paper presents the results of an experimental study of the structure, electrical, galvanomagnetic and thermoelectric properties of pure bismuth and Bi1−x Sbx thin films (x = 0.05 and 0.12) on a mica substrate in the thickness range of 10−30 nm. An increase in the conductivity with a decrease in the thickness of the samples was found. It may be due to the presence of topologically protected surface states. It is shown that the features of the manifestation of this effect are significantly influenced by the alloys band structure. The form of the temperature dependences of the Seebeck coefficient casts doubt on the fact that surface states have a positive effect on the thermoelectric efficiency of thin bismuth-antimony films. However, the detection of a positive thermoelectric power in Bi0.88Sb0.12 samples can become an important factor for searching for the possibility of creating a p-branch of thermoelectric converters.