Physical phenomena of the cage compounds RE3Pd20Si6 (RE = Yb, Lu)

Features of atomic rattling motion (anharmonic thermal vibrations), a phenomenon that relates to a new route for devising materials for thermoelectric applications of complex metal alloys, have been detected in certain members of the RE3Pd20X6 (RE = rare-earth element, X = Si or Ge) series of compounds relating to details of their particular crystal structure. In this work, thermal properties of Yb3Pd20Si6 and Lu3Pd20Si6 are reported as a first account of their position with respect to atomic rattling in an attempt to demystify the conditions that favour this dynamic materials property.