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Inelastic neutron scattering measurements on several Tl filled skutterudites (, , and ) all show a sharp peak in the vibrational density of states at , which is absent in the unfilled skutterudite . Heat capacity measurements on as compared to are consistent with the presence of a localized vibrational mode associated with the “rattling” thallium atoms in this filled skutterudite compound. Both results are well described by a localized Einstein mode model with an Einstein temperature of . These data provide perhaps the clearest example of local mode behavior in a concentrated metallic system.