  Theoretical analysis of the electronic structure of the high-entropy-type
superconductor (ScZrNb)$_{1-x}$(RhPd)$_x$, $x \in (0.35, 0.45)$ is presented.
The studied material is a partially ordered CsCl-type structure, with two
sublattices, randomly occupied by Sc, Zr, Nb (first sublattice) and Nb, Rh, and
Pd (second sublattice). Calculations were done using the Korringa-Kohn-Rostoker
method with the coherent potential approximation (KKR-CPA) and take into
account the substitutional disorder. Our total energy calculations confirm the
preference for the partially ordered structure over the fully random {\it
bcc}-type one. Electronic densities of states $N(E)$, dispersion relations, and
McMillan-Hopfield parameters $\eta$ (electronic contribution to electron-phonon
coupling) are studied as a function of composition. The computed increasing
trends in $N(E_F)$ and $\eta$ with $x$ are opposite to what we expected based
on the experimental results, where the decrease in the critical temperature
with increasing $x$ was found. Very strong electron scattering due to disorder
is observed, as the electronic dispersion relations are strongly smeared. As a
result, the computed electronic lifetimes $\tau$ are very short, leading to a
small mean-free path of electrons of the order of interatomic distance, which
puts (ScZrNb)$_{1-x}$(RhPd)$_x$ near the Mott-Ioffe-Regel limit. The trend in
$\tau(x)$ is similar to the trend observed experimentally in $T_c(x)$,
suggesting that disorder may be the factor that influences $T_c$ in this series
of alloys.

Superconductivity