Abstract
It was shown that delafossite oxide CuY2,33 prepared by solid-state reaction from the pelletized mixture of the nanopowders Y2O3 +2CuO, in air and at firing temperature 809-852 °C, obeys metallic properties. Upon cooling down to +39 °C, the metallic state undergoes a resistive transition, which suggests the first reproducible superconductivity appearing at a temperature higher than that of the ice melting temperature. Klein-Schwinger effect is suggested as a driving mechanism for the creation of electron-hole pairs. Electric properties are interpreted in terms of topological superconductivity.


