Superconductivity at 53.5 K in GdFeAsO1−δ

Here we report the fabrication and superconductivity of the iron-based arsenic oxide GdFeAsO 1−δ compound with oxygen-deficiency, which has an onset resistivity transition temperature at 53.5 K. This material has the same crystal structure as the newly discovered high- T c ReFeAsO 1−δ family (Re = rare earth metal) and a further reduced crystal lattice, while the T c starts to decrease compared with the SmFeAsO 1−δ system.