Electronic structure of novel multiple-band superconductor SrPt$_2$As$_2$

We present LDA calculated electronic structure of recently discovered superconductor SrPt$_2$As$_2$ with T$_c=5.2$ K. Despite its chemical composition and crystal structure are somehow similar to FeAs-based high-temperature superconductors, the electronic structure of SrPt$_2$As$_2$ is very much different. Crystal structure is orthorhombic (or tetragonal if idealized) and has layered nature with alternating PtAs$_4$ and AsPt$_4$ tetrahedra slabs sandwiched with Sr ions. The Fermi level is crossed by Pt-5d states with rather strong admixture of As-4p states. Fermi surface of SrPt$_2$As$_2$ is essentially three dimensional, with complicated sheets corresponding to multiple bands. We compare SrPt$_2$As$_2$ with 1111 and 122 representatives of FeAs-class of superconductors, as well as with isovalent (Ba,Sr)Ni$_2$As$_2$ superconductors. Brief discussion of superconductivity in SrPt$_2$As$_2$ is also presented.