On the resonant level of chromium in the rhombohedral and cubic phases of Pb$_{1-x-y}$Ge$_x$Cr$_y$Te alloys

The temperature dependences of the Hall coefficient (4.2 $\le T\le$ 300 K, $\mathbf{B}\le$ 0.07 T) in Pb$_{1-x-y}$Ge$_x$Cr$_y$Te alloys ($x$ = 0.03–0.08, $y\le$ 0.01) are studied. An increase in the absolute value of the Hall coefficient with an increase in temperature is found. This fact is indicative of a decrease in the concentration of free electrons as a result of the motion of the resonant level of chromium stabilizing the Fermi level relative to the conduction-band bottom. The temperature dependences of the Hall coefficient, in satisfactory agreement with the experimental ones, are calculated in the context of the two-band Kane dispersion law allowing for the structural phase transition upon increasing temperature. The energy position and temperature coefficients of the motion of the resonant level of chromium relative to the middle of the band gap in the rhombohedral and cubic phases are determined.