Superconductivity at 17 K in (Fe2P2)(Sr4Sc2O6): a new superconducting layered pnictide oxide with a thick perovskite oxide layer

A new layered pnictide oxide (Fe2P2)(Sr4Sc2O6) has been synthesized by solid-state reaction. This material has an alternating layer stacking structure of anti-fluorite Fe2P2 and perovskite-based Sr4Sc2O6 oxide layers. The space group of the material is P4/nmm and the lattice constants a and c are 4.016 and 15.543 A, respectively. The interlayer Fe–Fe distance corresponding to the c-axis length is the longest ever reported in the iron-based pnictides. In both magnetization and resistivity measurements, the present compound exhibited superconductivity below 17 K; this temperature is much higher than that for LaFePO and the highest in arsenic-free iron-based pnictide systems under ambient pressure.