Superconductivity in the metallic-oxidized magnesium interface
  Metastable superconductivity at 39 - 54 K in the interfaces formed by metallic and oxidized magnesium (MgO) has been observed by ac magnetic susceptibility measurements. The superconducting interfaces have been produced by the surface oxidation of metallic magnesium under special conditions. 
N.S. Sidorov, A.V. Palnichenko, S.S. Khasanov
cond-mat.supr-con