Hyperfine range (HFR) magnetic field ( H < 300 Oe) induced increase of photoconductivity and decrease of dark conductivity are observed in thin-layer sandwich type Autetrathiotetracene-A1 systems. The experimental results are interpreted in terms of HFR magnetic field influence on single-triplet transition rate of charge transfer (CT) states a t metal (Me)-organic semiconductor (0s) interface in the framework of Merrifield's et al.hyperfine interaction model. It is suggested that in the case of photoconductivity, triplet 3CT states are initially formed by molecular triplet exciton dissociation a t the Me-OS interface, whereas in the case of dark conductivity, singlet lCT states are initially formed in the process of non-equilibrium hole injection from the Me electrode. The HFR magnetic field reduces the lCT-3CT transition rate and is thus assumed to cause the observed increase of photo-and decrease of dark conductivity. The possible role of the inhomogeneous local magnetic field caused by the charge carriers trapped near the Me-OS interface on the rate of lCT"CT transition is also briefly discussed.