RuAl6An Endohedral Aluminide Superconductor

Superconductivity is reported in an endohedral aluminide compound, RuAl6, with T c = 1.21 K. The normalized heat capacity jump at T c, ΔC/γT c = 1.58, confirms bulk superconductivity. The Ginzburg–Landau parameter of κ = 9.5 shows that RuAl6 is a type-II superconductor. Electronic structure calculations for RuAl6 are explored in comparison to its structural analogue ReAl6 (T c = 0.74 K). The stability of the phases is discussed in terms of the crystal orbital Hamilton population (−COHP) analysis. The difference in T c in the two materials is caused by the significantly stronger electron–phonon coupling found in RuAl6, which is a result of significantly stronger antibonding interactions. The presence of superconductivity in yet another compound made of aluminum clusters possibly expands the correlation of critical temperature and the structure shown for Ga-built clusters.