High-entropy silicide superconductors with W${}_5$Si${}_3$-type structure

We report the synthesis, crystal structure and physical properties of two new high-entropy silicides (HESs), namely (Nb${}_{0.1}$Mo${}_{0.3}$W${}_{0.3}$Re${}_{0.2}$Ru${}_{0.1}$)${}_5$Si${}_3$ and (Nb${}_{0.2}$Mo${}_{0.3}$W${}_{0.3}$Re${}_{0.1}$Ru${}_{0.1}$)${}_5$Si${}_3$. Structural analysis indicates that both HESs consist of a (nearly) single tetragonal W${}_5$Si${}_3$-type phase (space group $I$4/$mcm$) with a disordered cation distribution. Electrical resistivity, magnetic susceptibility and specific heat measurements show that (Nb${}_{0.1}$Mo${}_{0.3}$W${}_{0.3}$Re${}_{0.2}$Ru${}_{0.1}$)${}_5$Si${}_3$ and (Nb${}_{0.2}$Mo${}_{0.3}$W${}_{0.3}$Re${}_{0.1}$Ru${}_{0.1}$)${}_5$Si${}_3$ are weakly coupled bulk superconductors, which represent the first superconducting high-entropy nonoxide ceramics. In particular, these HESs have higher $T_{\mathrm{c}}$ values (3.2-3.3 K) compared with those of the binary counterparts, and their $B_{\mathrm{c}2}$(0)/$T_{\mathrm{c}}$ ratios are the largest among superconductors of the same structural type.