Unconventional Superconductivity in the Layered Iron Germanide YFe2Ge2

The iron-based intermetallic YFe2Ge2 stands out among transition metal compounds for its high Sommerfeld coefficient of the order of 100 mJ/(mol K-2), which signals strong electronic correlations. A new generation of high quality samples of YFe2Ge2 show superconducting transition anomalies below 1.8 K in thermodynamic, magnetic, and transport measurements, establishing that superconductivity is intrinsic in this layered iron compound outside the known superconducting iron pnictide or chalcogenide families. The Fermi surface geometry of YFe2Ge2 resembles that of KFe2As2 in the high pressure collapsed tetragonal phase, in which superconductivity at temperatures as high as 10 K has recently been reported, suggesting an underlying connection between the two systems.