http://www.sciencemag.org/news/2019/11/next-graphene-shiny-and-magnetic-new-form-pure-carbon-dazzles-potential

Researchers believe films of U-carbon consist of stacks of undulating layers, tiled with six- or 12-atom rings and bound together by covalent bonds.

A “happy accident” has yielded a new, stable form of pure carbon made from cheap feedstocks, researchers say. Like diamond and graphene, two other guises of carbon, the material seems to have extraordinary physical properties. It is harder than stainless steel, about as conductive, and as reflective as a polished aluminum mirror. Perhaps most surprising, the substance appears to be ferromagnetic, behaving like a permanent magnet at temperatures up to 125°C—a first for carbon. The discovery, announced by physicist Joel Therrien of the University of Massachusetts in Lowell on 4 November here at the International Symposium on Clusters and Nanomaterials, could lead to lightweight coatings, medical products, and novel electronic devices.