The Manganites as Metallic Semiconductors
  The two-band model possessing metal and semiconductor properties is offered. This model may explain the appearance of temperature maximum of the electrical resistance at the proper relationships between the parameters of the theory. The calculations are carried in the tight-binding approximation. The applicability of the model to the manganites is discussed. 
Boris V. Karpenko and Alexander V. Kuznetzov
cond-mat.str-el