Abstract
In the case of 5f magnetism, the net increase of Tc due to the interstitial doping by hydrogen is generally understood as due to the increase of the density of states at the Fermi level, resulting from 5f band narrowing. The record value of Tc among UTX compound can be achieved in hydrides of U(Co,Fe)Sn series (Tc = 108 K for 15% of Fe).
This concept, based on the 5f band formed by periodic array of U sites, does not work for Th doped compounds. In the case of U sublattice diluted by a non-magnetic element the expansion cannot have dominant effect, partly because already doping by non-magnetic Th leads to an expansion.