  The planar interface of an isotropic homogeneous metal and an ambichiral
dielectric material can guide surface-plasmon-polariton waves. The planar
interface of an isotropic, homogeneous dielectric material and an ambichiral
dielectric material can guide Dyakonov-Tamm waves. In either instance, we found
that, as the ambichiral partnering material evolves into a finely chiral
material, the solutions of the dispersion equation for surface-wave propagation
evince convergence. The convergence is faster for the surface waves with larger
phase speeds than for the surface waves with smaller phase speeds.
