Fishtail Effect and the Upper Critical Field in a Superconducting Ca 1 0 (Pt 4 As 8 )(Fe 2 − x Pt x As 2 ) 5

A single crystal of a superconducting Ca10(Pt4 As8)(Fe2−xPtxAs2)5 (x = 0.01) was grown by the Bridgman method. The transition temperature was 32 K. The penetration field, H p , was measured and the superconducting parameters, κ, λ, and ξ, were obtained from H p . A fitting function was derived for the field dependence of the magnetization (M−H curve) including the fishtail effect and the secondary peak using a statistical method. The temperature dependence of the upper critical field, H c2, was obtained from the fitting function and H c2(0) was estimated to be 134 T. In addition, the SDW transition in the normal state is reported.