  We study theoretically the characteristics of surface waves excited at the
interface between a metal and a general bi-isotropic medium, which includes
isotropic chiral media and Tellegen media as special cases. We derive an
analytical dispersion relation for surface waves, using which we calculate the
effective index and the propagation length numerically. We also calculate the
absorptance, the cross-polarized reflectance and the spatial distribution of
the electromagnetic fields for plane waves incident on a bilayer system
consisting of a metal layer and a bi-isotropic layer in the Kretschmann
configuration, using the invariant imbedding method. The results obtained using
the invariant imbedding method agree with those obtained from the dispersion
relation perfectly. In the case of chiral media, the effective index is an
increasing function of the chirality index, whereas in Tellegen media, it is a
decreasing function of the Tellegen parameter. The propagation length for
surface waves in both cases increase substantially as either the chirality
index or the Tellegen parameter increases. In Tellegen media, it diverges to
infinity when the effective index goes to zero, whereas in chiral media, it
does when the parameters approach the cutoff values where quasi surface waves
are excited. We investigate the characteristics of quasi surface waves excited
when the chirality index is sufficiently large.
