-TlInSe2 is an analog of the TlSe binary compound, it has tetragonal structure with 18 the lattice parameters R = 8.02 % and C = 6.826 % and belongs to the Dqh (14/mcm) space group /I/.Elsewhere /2 to 4/ data were presented on new photoacoustical and piezophotoresistive effects found experimentally with TlInSe2 single crystals. Some photoelectric and optic characteristics of TlInSe2 were studied by other investigat o r s / 5 , 6/.The lack of literature data on the energy structure of TIInSea entailed us to offer this report in which we present the results of experimental investigations on the absorption edge and the temperature dependence of the electric conductivity.TlInSe2 compound was synthesized from thallium and indium monoselenide master alloys. Single crystals were grown by the Bridgman-Stockbarger method.Electrical measurements were carried out in the temperature range from 290 to Ti00 K by the method described in another report /7/, Photoconductivity measurements were carried out by means of an SPM-2-type monochromator (GDR) with a Si02 prism at a slit width of 0.02 to 0.08 mm. The signal was amplified by an YI-2-type amplifier. type spectroyhotometers, a s well a s by means of YM-2-type monochromator. All measurements were carried out at 300 K with the incident radiation perpendicular to the C-axis. The thickness of the specimens varied between 40 and 200 p m . The absorption coefficient ( a~ ) was calculated from transmission and reflection data by the method presented elsewhere /8/.Optical measurements were performed with the use of In the earlier study /1/ a value of 1.12 eV and in another study /2/ a value of 1.2 eV were obtained for the width of the forbidden gap on the basis of the temperature dependence of the conductivity and the Hall effect. Our investigations have shown that in the temperature range from 300 to 480 K the activation energies a r e in good agreement with the published daka. A s the direction of the current in a specimen is changed from that parallel to the crystallographic C-axis to that

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