Conductivity, weak ferromagnetism and charge instability in $\alpha-MnS$   single crystal
  The temperature dependence of resistivity, magnetization and electron-spin resonance of the $\alpha- MnS $ single crystal were measured in temperature range of $5 K < T < 550 K$. Magnetization hysteresis in applied magnetic field up to 0.7 T at $T=5 K, 77 K, 300 K$, irreversible temperature behavior of magnetization and resistivity were found . The obtained data were explained in terms of degenerate tight binding model using random phase approximation. The contribution of holes in $t_{2g}$ and $e_g$ bands of manganese ions to the conductivity, optical absorbtion spectra and charge instability in $\alpha -MnS $ were studied. Charge susceptibility maxima resulted from the competition of the on-site Coulomb interaction between the holes in different orbitals and small hybridization of sub-bands were calculated at $T=160 K, 250 K, 475 K$. 
S.S. Aplesnin, L. I. Ryabinkina, G. M. Abramova, O.B. Romanova, A.M.   Vorotynov, D.A. Velikanov, N. I. Kiselev, A. D. Balaev