We report magnetic susceptibility measurements on a layered superconductor Li0.48(THF)0.3HfNCl having Tc approximately 26 K. The present study revealed that (a) the Fermi level density of states is small, N*(EF) approximately 0.25 states/(eV spin f.u.), (b) mass enhancement is negligible, gamma; approximately 1, (c) electron-phonon coupling is weak, lambda(ep)<<1, (d) exchange enhancement is negligible, 1/(1+F(a)0) approximately 1, and (e) electronic density parameter is large, r(2D)s approximately 10.3 (i.e., low-carrier density). It is difficult to explain the origin of the high Tc in terms of the conventional phonon (BCS) mechanism of superconductivity.

Dc-magnetization and NMR measurements were carried out on a layered superconductor Li 0.48 (THF) y HfNCl having T c ϳ26 K. For the magnetic field applied perpendicular to the basal plane (ab plane͒ above 10 kOe, we found a pronounced broadening of the superconducting transition in temperature dependence of magnetization and the substantial diamagnetic signals were observed as high as 2T c , indicating the existence of superconducting fluctuations. Analysis based on the anisotropic Ginzburg-Landau model reveals that the present system is a highly anisotropic superconductor. 7 Li-NMR signals were observed around zero Knight shift, indicating that the local Fermi-level density of states, N(E F), at Li site is practically nothing and the superconductivity is derived from the HfNCl layer. We have shown the unambiguous evidence for the quasi-two-dimensional superconducting character in this system.

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