  BaPb$_{1-x}$Bi$_x$O$_3$ is a superconductor, with transition temperature
$T_c=11$ K, whose parent compound BaBiO$_3$ possess a charge ordering phase and
perovskite crystal structure reminiscent of the cuprates. The lack of magnetism
simplifies the BaPb$_{1-x}$Bi$_{x}$O$_3$ phase diagram, making this system an
ideal platform for contrasting high-$T_c$ systems with isotropic
superconductors. Here we use high-quality epitaxial thin films and
magnetotransport to demonstrate superconducting fluctuations that extend well
beyond $T_c$. For the thickest films (thickness above $\sim100$ nm) this region
extends to $\sim27$ K, well above the bulk $T_c$ and remarkably close to the
higher $T_c$ of Ba$_{1-x}$K$_x$BiO$_3$ ($T_c=31$ K). We drive the system
through a superconductor-insulator transition by decreasing thickness and find
the observed $T_c$ correlates strongly with disorder. This material manifests
strong fluctuations across a wide range of thicknesses, temperatures, and
disorder presenting new opportunities for understanding the precursor of
superconductivity near the 2D-3D dimensionality crossover.

Superconductivity