Crystal twinning plane - superconducting two-dimensional metal

The superconductivity effect of a tin crystal twinning plane (301) is discovered. The effect takes place at a temperature Tsub(c) < T < Tsub(c) + 0.15 K and in a magnetic field H < 5 Oe. To explain the effect we introduce an idea of 'two-dimensional metal' consisting of: a twinning plane crystal lattice; a two-dimensional group of electrons moving parallel to the twinning plane; two-dimensional twinning plane phonons. Electronic properties of a thin 'two-dimensional metal' layer differs from electronic properties of a bulk mother crystal twins. (orig.)