Novel pressure-induced interactions in silane-hydrogen.

We report novel molecular compound formation from silane-hydrogen mixtures with intermolecular interactions unprecedented for hydrogen-rich solids. A complex H_{2} vibron spectrum with anticorrelated pressure-frequency dependencies and a striking H-D exchange below 10 GPa reveal strong and unusual attractive interactions between SiH_{4} and H_{2} and molecular bond destabilization at remarkably low pressure. The unique features of the observed SiH_{4}(H_{2})_{2} compound suggest a new range of accessible pressure-driven intermolecular interactions for hydrogen-bearing simple molecular systems and a new approach to perturb the hydrogen covalent bond.