Superconductivity at 38 K in Iron-Based Compound with Platinum--Arsenide Layers Ca10(Pt4As8)(Fe2-xPtxAs2)5

We report superconductivity in novel iron-based compounds Ca 10 (Pt n As 8 )(Fe 2-x Pt x As 2 ) 5 with $n = 3$ and 4. Both compounds crystallize in triclinic structures (space group $P\bar{1}$), in which Fe 2 As 2 layers alternate with Pt n As 8 spacer layers. Superconductivity with a transition temperature of 38 K is observed in the $n = 4$ compound with a Pt content of $x\simeq 0.36$ in the Fe 2 As 2 layers. The compound with $n = 3$ exhibits superconductivity at 13 K.