Glassy to Icosahedral Phase Transformation in Pd-U-Si Alloys

We observe for the first time the transformation of glassy alloys (${\mathrm{Pd}}_{100-x-y}{\mathrm{U}}_x{\mathrm{Si}}_y$, $x\simeq y\simeq 20$ at.%) into a metastable icosahedral phase with quasicrystalline order upon annealing. The icosahedral symmetry of the latter phase is confirmed by x-ray and electron diffraction. This phase can be formed only within a very narrow compositional range (< 2 at.%) of U and Si, suggestive of a strong chemical ordering in it. The icosahedral and glassy phases have similar electrical transport properties. However, magnetic-susceptibility results indicate that the electronic structure of the icosahedral phase is very different from its glassy and crystalline (U${\mathrm{Pd}}_3$) counterparts.