resistance: New superconductors contain alternating layers of iron arsenide (orange and red) and rare earth metal oxides (blue and gray) doped with fluorine (green). Iron arsenide compounds become superconducting at relatively high temperatures of 55 K, and researchers are now beginning to decipher their superconducting mechanism. A new class of high-temperature superconductors, discovered earlier this year, behaves very differently than previously known copper-oxygen superconductors do. Instead, the new materials seem to follow a superconductivity mechanism found previously only in materials that are superconducting at very low temperatures, Chia-Ling Chien and his colleagues at Johns Hopkins University report in an online Nature paper.