  The kagome lattice is a fertile platform to explore topological excitations
with both Fermi-Dirac and Bose-Einstein statistics. While relativistic Dirac
Fermions and flat-bands have been discovered in the electronic structure of
kagome metals, the spin excitations have received less attention. Here we
report inelastic neutron scattering studies of the prototypical kagome magnetic
metal FeSn. The spectra display well-defined spin waves extending up to 120
meV. Above this energy, the spin waves become progressively broadened,
reflecting interactions with the Stoner continuum. Using linear spin wave
theory, we determine an effective spin Hamiltonian that reproduces the measured
dispersion. This analysis indicates that the Dirac magnon at the K-point
remarkably occurs on the brink of a region where well-defined spin waves become
unobservable. Our results emphasize the influential role of itinerant carriers
on the topological spin excitations of metallic kagome magnets.
