  It has been suggested that hydrogen may metallise at lower pressures if it is
``precompressed''. Here we introduce a search strategy for predicting
high-pressure structures and apply it to silane using first-principles
electronic structure computations. It is based on relaxing randomly chosen
structures, and is demonstrated to work well for unit cells containing up to at
least ten atoms. We predict that silane will metallise at higher pressures than
previously anticipated, but we suggest that the metallic phase might show
high-temperature superconductivity at experimentally accessible pressures.
