Wikipedia
Niobium-tin (NbSn) or triniobium-tin is a metallic chemical compound of niobium (Nb) and tin (Sn), used industrially as a type II superconductor. This intermetallic compound is an A15 phase superconductor. It is more expensive than niobium-titanium (NbTi), but remains superconducting up to a magnetic flux density of 30 teslas (T), compared to a limit of roughly 15 T for NbTi.
NbSn was discovered to be a superconductor in 1954. The material's ability to support high currents and magnetic fields was discovered in 1961 and started the era of large-scale applications of superconductivity.
The critical temperature is 18.3 kelvins (K). Application temperatures are commonly around 4.2 K, the boiling point of liquid helium at atmospheric pressure.
In April 2008 a record non-copper current density was claimed of 2643 A/mm² at 12 T and 4.2 K