Superconductivity in the intermetallic compound Zr₅Al₄

Polycrystalline Zr₅Al₄ was synthesized using the arc-melting method. Powder X-ray diffraction confirms the previously reported crystal structure of the Ti₅Ga₄-type () with lattice parameters: a = 8.4312(6) A°, and c = 5.7752(8) AA°. Electrical resistivity and low-temperature magnetic susceptibility measurements indicate that Zr₅Al₄ exhibits superconducting behavior below 2 K. The normalized heat capacity jump at T_c = 1.82 K, δC/γT_c = 1.50, confirms the bulk superconductivity. The Sommerfeld coefficient γ = 28.5 mJ mol^-1K^-2 and the Debye temperature Θ_D = 320 K were obtained by fitting the low-temperature heat capacity data. The electron-phonon coupling strength λ_el-ph = 0.49 and estimated upper critical field μ₀H_c2(0) = 1.09 T (dirty limit) suggest that Zr₅Al₄ is a weakly coupled type-II superconductor. First-principles calculations show the presence of a van Hove singularity near the Fermi energy.