Superconductivity at 52 K in iron-based F-doped layered quaternary   compound Pr[O1-xFx]FeAs
  Since the discovery of copper oxide superconductor in 1986 [1], extensive efforts have been devoted to the search of new high-Tc superconducting materials, especially high-Tc systems other than cuprates. The recently discovered quaternary superconductor La[O1-xFx]FeAs with the superconducting critical transition Tc of 26 K [2], which has a much simple layered structure compared with cuprates, has attracted quick enthusiasm and is going to become a new high-Tc system [3-6]. Here we report the discovery of bulk superconductivity in the praseodymium-arsenide oxides Pr[O1-xFx]FeAs with an onset drop of resistivity as high as 52 K, and the unambiguous zero-resistivity and Meissner transition at low temperature, which will place these quaternary compounds to another high-Tc superconducting system explicitly. 
Zhi-An Ren, Jie Yang, Wei Lu, Wei Yi, Guang-Can Che, Xiao-Li Dong,   Li-Ling Sun, Zhong-Xian Zhao