The charge transport mechanism in a new magnetic topological insulator MnBi$_{0.5}$Sb$_{1.5}$Te$_{4}$

A new layered magnetic topological insulator with the composition MnBi$_{0.5}$Sb$_{1.5}$Te$_{4}$ is obtained. The electrical conductivity in the plane of the layers and in the direction normal to the layers is studied in the range of temperatures of 1.4 – 300 K. It is found that a “metallic” character of the temperature dependence of the resistivity $\rho(T)$ is observed in the range of temperatures of 50 – 300 K in both directions. Below $T$ = 50 K, the value of $\rho$ increases and demonstrates an uncommon temperature dependence with a characteristic feature in the region of the critical temperature $T_c$ = 23 K. The increase in the resistance in the temperature range of 50 – 23 K is determined by the spin fluctuations and magnetic phase transition. Below $T_c$ and down to 1.4 K, $\rho(T)$ demonstrates a behavior characteristic for the weak localization effect, which is confirmed by the analysis of the data obtained when studying magnetoresistance.