Tessier-Ashpool S.A.
The surface of a neutron star is made of iron. In the presence of a strong magnetic field the atoms of iron polymerize. The polymers pack to form a lattice with density about ten thousand times that of terrestrial iron and strength a million times that of steel.
Wikipedia
P6280392 by roel.ubels on Flickr.

P6280392 by roel.ubels on Flickr.