Elemental complexity

Science: Metals are solids in which conduction electrons remain mobile even at absolute zero temperature. In a semimetal, the concentration of such mobile electrons is extremely low. Whereas in a typical metal, say copper, there is roughly one itinerant electron per atom, in bismuth, the archetypal semimetal, 100,000 atoms share a single mobile electron. On the July 25 issue of Science, Li et al. report that in the presence of a strong magnetic field, this dilute electron gas orders in a way never observed in any other material.