In the present paper, we give a summary of our recent studies of photoelectric properties of Pb1-xSnxTe:In (LTT) films grown on BaF2 substrates. The data, obtained at helium temperatures, were analyzed considering an important role of injection of electrons out of contacts and their capture at traps in the films, forming conditions under which the electrical conduction in the samples was dominated by space-charge-limited injection currents [1-3]. LTT films with compositions x=0.24-0.28 were examined. The films were doped with indium to 3 at. %, with their thickness being about 1 μm, and their specific resistance r at T=4.2 K, greater than 108 W·cm. A high mobility of charge carriers in LTT, m > 104 cm2·V-1·s-1, and a high dielectric permittivity of the material, e > 2000, have allowed us to measure injection currents in «planar» structures with 0.1-cm inter-electrode separation. Using such structures, we were able to organize uniform illumination of the inter-contact region both with radiation in the fundamental absorption band and with radiation in the submillimeter region of the spectrum, this being not possible with structures prepared on bulk single crystals. As the source of radiation, the freeelectron laser (FEL) of the Siberian Center of Photochemical Studies and Technologies was used, whose tunable emission wavelength was varied in the interval l » 70-220 μm.Fig. 1. Photocurrent rise at various bias voltages U, Volt: 0.012 (1), 0.026 (2), 0.047 (3), 0.092 (4), 0.21 (5), 0.41 (6), 0.82 (7), 1.5 (8), 3.0 (9). The time at which the illumination was turned on is indicated by upward arrows , and the time at which the illumination was turned off, by downward arrows ¯.Figure 1 shows current-vs-time curves of an LTT sample measured on exposing this sample at T=4.2 K to FEL radiation of wavelength l = 123 μm (quantum energy hn = 0.01 eV) at different bias voltages. The complex multi-step behavior of the current rise in the FEL-illuminated sample, including the presence of current oscillations in the curves (see curves 4-7, t » 2050 s), could be qualitatively explained on the assumption that a quasi-continuous distribution of electron traps was present in the samples [3]. The data obtained are also in agreement with current oscillations observed in samples under no-illumination conditions. Also, data showing how the transmission of the LTT films in the THz spectral region varied with increasing bias voltages (up to U » 100 V, E » 1000 V/cm) are reported. A schematic of a test structure for such measurements and its current-voltage characteristics at T = 4.2 K are shown in Fig. 2.Fig. 2. Schematic of the test structure for measuring the transmission of an LTT film in the THz spectral region and the current-voltage characteristics of the structure. The voltage UFFT is indicated by an arrow.The voltage UFFT at which the deep traps in the sample became completely filled with electrons is indicated with the arrow. The observed variation of the transmission was due to different occupations of traps with a distributed energy spectrum at different bias voltages.