Pr4Fe2As2Te1-xO4: A layered FeAs-based superconductor

We report crystal growth at high pressure, structure determination, and magnetic and transport studies of an oxypnictide superconductor Pr4Fe2As2Te1-xO4. Its structure resembles the known 1111 phase except for the considerably larger c lattice constant and intercalated tellurium atoms and it crystallizes in a tetragonal lattice [a = 4.0165(2) angstrom, c = 29.8572(16) angstrom, and space group I4/mmm (no. 139)]. The electrical resistivity rho(T) and magnetization measurement show a transition at T-c approximate to 25 K. The lower (H-c1) and upper (H-c2) critical fields are 2 mT and 6.5 T, respectively. The Ginzburg- Landau parameter of kappa approximate to 80 places this compound in the family of strong type-II superconductors.