Discovery and Implications of Hidden Atomic-Scale Structure in a Metallic Meteorite

[Image: see text] Iron and its alloys have made modern civilization possible, with metallic meteorites providing one of the human’s earliest sources of usable iron as well as providing a window into our solar system’s billion-year history. Here highest-resolution tools reveal the existence of a previously hidden FeNi nanophase within the extremely slowly cooled metallic meteorite NWA 6259. This new nanophase exists alongside Ni-poor and Ni-rich nanoprecipitates within a matrix of tetrataenite, the uniaxial, chemically ordered form of FeNi. The ferromagnetic nature of the nanoprecipitates combined with the antiferromagnetic character of the FeNi nanophases gives rise to a complex magnetic state that evolves dramatically with temperature. These observations extend and possibly alter our understanding of celestial metallurgy, provide new knowledge concerning the archetypal Fe–Ni phase diagram and supply new information for the development of new types of sustainable, technologically critical high-energy magnets.