  We have discovered superconductivity in the two-layer semiconducting
monochalcogenide heterostrutures PbTe/PbS, PbTe/PbSe and PbTe/YbS. By comparing
data from two-layer samples with data from single monochalcogenide films we
conclude that the superconductivity is connected with the interface between the
two semiconductors. Evidence for the low dimensional nature of the
superconducting interlayer is presented and a model that explains the
appearance of single-interface superconductivity is proposed.
