Antitaenite

Antitaenite is a meteoritic metal alloy mineral composed of iron and 20–40% nickel, that has a face centered cubic crystal structure.
There are three other known Fe-Ni meteoritic minerals: kamacite, taenite, and tetrataenite.
The existence of antitaenite as a new mineral species, occurring in both iron meteorites and in chondrites, was first proposed in 1995 but the IMA has not approved paramagnetic antitaenite; instead the organization regards it as a variety of taenite. Gamma Fe-Ni alloys with low-Ni are probably inhomogeneous on a nanometer scale.
Antitaenite and taenite have the same crystal structure and can have the same chemical composition but they differ in their electronic structures: taenite has a high magnetic moment whereas antitaenite has a low magnetic moment. This difference in electronic structure was first established in 1999 and arises from a high-magnetic-moment to low-magnetic-moment transition occurring in the Fe-Ni bi-metallic alloy series. The same electronic structure transition is believed to be a causal factor in Invar behaviour.