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Phonon dispersion curves were obtained from inelastic x-ray and neutron scattering measurements on -uranium single crystals at temperatures from 298 to 573 K. Both measurements showed a softening and an abrupt loss of intensity in the longitudinal optic branch along above 450 K. Above the same temperature a new dynamical mode of comparable intensity emerges along the zone boundary with energy near the top of the phonon spectrum. The new mode forms without a structural transition but coincides with an anomaly in the mechanical deformation behavior. We argue that the mode is an intrinsically localized vibration and formed as a result of a strong electron-phonon interaction.