  We report measurements and analysis of magnetization, resistivity and
thermopower of polycrystalline samples of the perovskite-type Co/Rh oxide
La$_{0.8}$Sr$_{0.2}$Co$_{1-x}$Rh$_x$O$_{3-\delta}$. This system constitutes a
solid solution for a full range of $x$,in which the crystal structure changes
from rhombohedral to orthorhombic symmetry with increasing Rh content $x$. The
magnetization data reveal that the magnetic ground state immediately changes
upon Rh substitution from ferromagnetic to paramagnetic with increasing $x$
near 0.25, which is close to the structural phase boundary. We find that one
substituted Rh ion diminishes the saturation moment by 9 $\mu_B$, which implies
that one Rh$^{3+}$ ion makes a few magnetic Co$^{3+}$ ions nonmagnetic (the low
spin state), and causes disorder in the spin state and the highest occupied
orbital. In this disordered composition ($0.05\le x \le 0.75$), we find that
the thermopower is anomalously enhanced below 50 K. In particular, the
thermopower of $x$=0.5 is larger by a factor of 10 than those of $x$=0 and 1,
and the temperature coefficient reaches 4 $\mu$V/K$^2$ which is as large as
that of heavy-fermion materials such as CeRu$_2$Si$_2$.
