Superconductivity with a high upper critical field in an equiatomic high-entropy alloy Sc–V–Ti–Hf–Nb.

High-entropy alloy (HEA) superconductors have attracted significant attention as an unconventional alloy class composed of five or more elements in significant ratios due to their remarkable mechanical, physical, and thermal properties. Superconducting HEAs combine the mechanical properties of HEAs with the quantum phenomenon of superconductivity, exhibiting high upper critical fields, robust critical current density, and retention of superconductivity under extreme conditions. In this study, we synthesize and characterize the equiatomic HEA Sc-V-Ti-Hf-Nb, which forms a body-centered cubic (bcc) structure with a transition temperature (Tc) of 4.17(3) K. The alloy exhibits weakly coupled, fully gapped type II superconductivity, with an upper critical field exceeding the Pauli paramagnetic limit, suggesting unconventional behavior. Furthermore, microscopic investigation has also been conducted to understand the pairing mechanisms in these materials. Our findings highlight the potential of HEAs for superconducting device applications in harsh environments, as their equiatomic composition maximizes disorder and provides opportunities to tailor superconducting properties.