Iron-based superconductivity was discovered in 2006, and in 2008 fluorine-doped LaFeAsO — replacing up to 11% of the oxygen with fluorine — became superconductive at 26 K.
Replacing lanthanum with rare-earth metals such as cerium and neodymium raises Tc to 52 K, and the 1111-type Sr₀.₅Sm₀.₅FeAsF holds the listed family maximum of 56 K.
In 2015, monolayer films of the related 11-type iron selenide on strontium titanate showed a Tc of around 105–111 K.