Experimental lattice dependence of the density of states in alkali fullerides

Using electron-spin resonance, we measured conduction-electron-spin susceptibility versus temperature for three alkali-fulleride compounds in the normal state. Converting the observed Pauli-spin susceptibility into density of states at the Fermi level N(0) and using the temperature dependence of the lattice parameter we fit the experimental variation of N(0) as a function of the inter-C-60 distance d with an exponential functional form. Assuming a universal T-c dependence on the lattice constant for every alkali fulleride, we used the value Ni(0)=f(d) in the Mcmillan formula fit the (T-c,d) data points taken from the literature.