  Analogous to the Hall effect, the Nernst effect is the generation of a
transverse voltage due to a temperature gradient in the presence of a
perpendicular magnetic field. The Nernst effect has promise for thermoelectric
applications and as a probe of electronic structure. In magnetic materials, a
so-called anomalous Nernst effect (ANE) is possible in zero magnetic field.
Here we report a colossal ANE reaching 23 $\mu$V/K in the ferromagnetic metal
UCo$_{0.8}$Ru$_{0.2}$Al. Uranium's $5f$ electrons provide strong electronic
correlations that lead to narrow bands, which are a known route to producing a
large thermoelectric response. Additionally, the large nuclear charge of
uranium generates strong spin-orbit coupling, which produces an intrinsic
transverse response in this material due to the Berry curvature associated with
the relativistic electronic structure. Theoretical calculations show that at
least 148 Weyl nodes and two nodal lines exist within $\pm$ 60 meV of the Fermi
level in UCo$_{0.8}$Ru$_{0.2}$Al. This work demonstrates that magnetic actinide
materials can host strong Nernst and Hall responses due to their combined
correlated and topological nature.
