Fig. 5.

(A) Resistivity between 2 K and 300 K of the HEA ${\left[\text{TaNb}\right]}_{1-x}{\left(\text{ZrHfTi}\right)}_x$ with x = 0.5. A, Inset shows the magnetic field dependence of the superconducting transition in fields from ${\mu }_{0}H=$ 0 T to 9 T in steps of 0.5 T. The dotted line displays the 50% criterion, which is commonly used for the determination of the upper critical field $H_{\text{c}2}.$ (B) Temperature dependence of the upper critical field $H_{\text{c}2},$ determined by the 50% criterion, of the ${\left[\text{TaNb}\right]}_{1-x}{\left(\text{ZrHfTi}\right)}_x$ HEAs with x = 0.30, 0.33, 0.35, 0.5, and 0.84. The lines are linear fits for determination of ${\left(d{H}_{\text{c}2}/dT\right)}_{T=T_{\text{c}}}.$