In 1911 Kammerlingh Onnes made the astonishing discovery that lead loses the last vestige of its electrical resistance when cooled below 7.2 K; a current flowing through a ring of lead in its superconducting state could go on flowing forever. Only a few months later Onnes discovered that this happy state has a natural enemy—magnetism. Until recently every new superconductor discovered was prey to an external magnetic field. The existence of a critical field that destroys superconductivity could be neatly explained in terms of the microscopic theory of superconductivity proposed by John Bardeen, Leon Cooper and J. Robert Schrieffer in 1957. Nevertheless a pair of theorists speculated that, given the right set of conditions, a magnetic field could actually induce a superconducting state. Such speculation was greeted with widespread skepticism, but last year a group of researchers from the University of Geneva and the Max Planck Institute in Grenoble found a substance that apparently exhibits precisely the behavior predicted by the theorists. More recently a group from Temple University, Boston University and Los Alamos reported the discovery of a material that apparently exhibits, in addition to a host of other exotic properties, magnetic‐field‐induced superconductivity.

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