  A TiS$_{2}$ crystal with a layered structure was found to have a large
thermoelectric power factor.The in-plane power factor $S^{2}/ \rho$ at 300 K is
37.1~$\mu$W/K$^{2}$cm with resistivity ($\rho$) of 1.7 m$\Omega$cm and
thermopower ($S$) of -251~$\mu$V/K, and this value is comparable to that of the
best thermoelectric material, Bi$_{2}$Te$_{3}$ alloy. The electrical
resistivity shows both metallic and highly anisotropic behaviors, suggesting
that the electronic structure of this TiS$_{2}$ crystal has a
quasi-two-dimensional nature. The large thermoelectric response can be ascribed
to the large density of state just above the Fermi energy and inter-valley
scattering. In spite of the large power factor, the figure of merit, $ZT$ of
TiS$_{2}$ is 0.16 at 300 K, because of relatively large thermal conductivity,
68~mW/Kcm. However, most of this value comes from reducible lattice
contribution. Thus, $ZT$ can be improved by reducing lattice thermal
conductivity, e.g., by introducing a rattling unit into the inter-layer sites.
