  We have systematically studied the structural and physical properties of the
superconducting hydrated Lix(H2O)yTaS2. The powder X-ray diffraction patterns
suggest that all the samples are single-phase compounds, and the crystal
structure is similar to that of 2H-TaS2. The transition temperature to
superconductivity shows a dome-shape dependence on the lithium content x with a
maximum Tc of 4.6 K for x=0.42, which is larger than in corresponding optimally
doped 2H-TaS2 superconductors without water or organic intercalants (Tc ~ 4.2
K). There are no signs for a charge-density-wave formation in hydrated
Lix(H2O)yTaS2. While our magnetic data indicate a rather strongly type-II
behavior, heat-capacity measurements reveal, like in other 2H-TaS2-type
compounds. From the corresponding Sommerfeld constants and Debye temperatures,
we can derive the parameter describing the electron-phonon coupling and the
electron density of states DOS(EF) at the Fermi level as functions of x. While
the variation of the DOS(EF) is consistent with that of Tc, indicating that the
lithium intercalation is tuning Tc via changing the DOS(EF) in
2H-Lix(H2O)yTaS2, the simultaneous changes of electron-phonon coupling and
Debye temperatures may also play a certain role.
