Resonant state of 4f^{14/13} Yb Ion in Pb_{1-x}Ge_{x}Te

The study of transport and of magnetic properties of Pb1-xGexTe:Yb mixed crystals (0 = x = 0.04) is reported. It is shown that Yb forms a donor state resonant with the PbTe valence band. The donor state position may be tuned (shifted relative to the energy gap) by admixture of Ge. The properties of the Yb ion in the Pb1-xGexTe matrix makes the system unique from the point of view of magnetic properties. It is demonstrated that the change of the conductivity type from p to n induces transitions from the paramagnetic state to the diamagnetic one