[en] The Schottky-like anomaly observed in Lu-H alloys containing 0.035 to approximately 2.0 at. percent H is due to H tunneling between various configurations of ''H--other interstitial'' (N, O and possibly C) pairs formed in Lu. As the H content increases beyond 2.0 at. percent, the formation of di-hydrogen--other interstitial groups is thought to prevent tunneling