13C nuclear-magnetic-resonance (NMR) spectra are obtained to investigate the electronic properties of a superconducting fulleride K3C60. Asymmetric line shapes below 235 K are reproduced by the powder patterns of anisotropic NMR frequency shifts (K1) of electronic single-site. The temperature (T) dependence of K1 indicates that the 13C hyperfine coupling (Aspin) has both an isotropic part (Aisospin) and an anisotropic part (Aaxspin) with Aisospin/Aaxspin = 0.78. Substantial decrease in the spin susceptibility (i.e. Xspin(Tc)/Xspin(300K) = 0.55) is not explained by the lattice contraction alone. The Knight shift values can be deduced experimentally without assuming the chemical shift values, since our analysis shows that the line shapes below Tc are affected negligibly by the magnetic-field distribution, which is consistent with the large penetration depth. We also showed the validity and consistency of our analysis.
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