  Symmetry breaking in topological matter became, in the last decade, a key
concept in condensed matter physics to unveil novel electronic states. In this
work, we reveal that broken inversion symmetry and strong spin-orbit coupling
in trigonal \ce{PtBi2} lead to a Weyl semimetal band structure, with unusually
robust two-dimensional superconductivity in thin fims. Transport measurements
show that high-quality \ce{PtBi2} crystals are three-dimensional
superconductors ($T_\text{c}\simeq $600~mK) with an isotropic critical field
($B_\text{c}\simeq $50~mT). Remarkably, we evidence in a rather thick flake
(60~nm), exfoliated from a macroscopic crystal, the two-dimensional nature of
the superconducting state, with a critical temperature $T_\text{c}\simeq
370$~mK and highly-anisotropic critical fields. Our results reveal a
Berezinskii-Kosterlitz-Thouless transition with $T_\text{BKT}\simeq 310$~mK and
with a broadening of Tc due to inhomogenities in the sample. Due to the very
long superconducting coherence length $\xi$ in \ce{PtBi2}, the
vortex-antivortex pairing mechanism can be studied in unusually-thick samples
(at least five times thicker than for any other two-dimensional
superconductor), making \ce{PtBi2} an ideal platform to study low dimensional
superconductivity in a topological semimetal.
