High-entropy alloys provide an ideal platform for investigating superconductivity in the presence of extreme chemical disorder, lattice distortion, and magnetic impurity effects. Herein, we report a systematic study of the structural, normal-state, and superconducting-state properties of ${\left(\text{TiVTa}\right)}_{0.6}{\text{Nb}}_{0.4-x}{\text{Cr}}_x$ high-entropy alloys with $x=0$, 0.05, and 0.20. All compositions crystallize in a single-phase body-centered-cubic structure, with space group Im-$3m$. Our detailed analysis includes magnetization, resistivity, and specific-heat capacity measurements. The superconducting transition temperature is progressively suppressed from 4.68 to 2.59 K and the upper critical field is decreased from 5.77 to 3.87 T with increasing Cr content in the structure. Heat capacity measurements confirm $s$-wave weak-coupling superconductivity with a superconducting gap within the BCS limit in all the materials. The suppression of transition temperature follows Abrikosov-Gor'kov behavior, identifying magnetic impurity scattering from Cr as the dominant pair breaking mechanism. First-principles calculation reveals severe local lattice distortion characterized by a large atomic size mismatch $\delta =5.5\%$ and a substantial average atomic displacement $(\mathrm{\Delta }d=0.22\AA )$. The interatomic distance distribution exhibits broadened coordination shells with partially filled gaps between nearest-neighbor shells, reflecting strong deviations from ideal lattice positions while retaining long-range crystalline order.

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• Magnetic susceptibility
• Superconductivity
• Crystal structures
• Superconductors