Experimental photocurrent-voltage characteristics of higher manganese silicide (HMS)--HMS and HMS--M structures have been analysed. The mechanism is considered of current flow under illumination with radiation. In the structures under study, the space-charge-limited-current (SCLC) mode is realized in the temperature interval 77-270 K, and photocurrent-voltage characteristics show regions of linear and quadratic dependence and a region of steep current rise. The high photosensitivity of these structures and the occurrence of SCLC is explained by (i) formation, in the subsurface region of Si diffusion-doped with manganese, of a contact layer of HSM injecting holes into silicon; and (ii) the fact that at low temperature the high-resistance base region of the structures illuminated with intrinsic radiation becomes a low-resistance conducting layer, and a transition layer in which the SCLC mode is realized is formed at the HMS- phase boundary.