59Co-NMR Knight Shift of Aligned Crystals and Polycrystalline Samples of   Superconducting Na0.3CoO2.1.3H2O
  Temperature (T) dependence of 59Co-NMR Knight shifts K of Na0.3CoO2.1.3H2O has been studied, where samples of randomly oriented powder and aligned crystals have been used for the applied magnetic fields H // ab plane and H //c-axis, respectively. For both directions of H, the shift K decreases below the superconducting transition temperature Tc(H) with decreasing T, indicating that the superconducting electron pairs are in the singlet state. The upper critical fields Hc2(T) determined from the K(H)-T curves are found to be consistent with the values reported by the resistivity measurements for both directions of H. 
Yoshiaki Kobayashi, Hidekazu Watanabe, Mai Yokoi, Taketo Moyoshi,   Yoshihiko Mori and Masatoshi Sato