Composite semiconductors belonging to the group A1B5C6(Ag3SbS3, Tl3SbS3, Ag3AsS3 and others) are seemed to be among the most promising materials for manufacturing detectors of ionizing radiations (γ-Ray Detectors Based on Composite A1B5C6 Semiconductors, H. Khlyap et al., MRS Proceed. 792 (2004, R3.4.1). Electric properties of these wide-gap semiconductors are almost not studied. The paper reports first experimental results on electric field-induced effects observed in these nanoscaled semiconductor structures under the room temperature. Bulk materials as well as thin films were studied. The experimental data were analyzed according to the semiclassical theory of tunneling in solids.