  We report 59Co NMR studies on the magnetically oriented powder samples of
Co-oxide superconductors NaxCoO2yH2O with Tc ~ 4.7 K. From two-dimensional
powder pattern in the NMR spectrum, the ab-plane Knight shift in the normal
state was estimated by the magnetic field dependence of second-order quadrupole
shifts at various temperatures. Below 50 K, the Knight shift shows a
Curie-Weiss-like temperature dependence, similarly to the bulk magnetic
susceptibility chi. From the analysis of so-called K-chi plot, the spin and the
orbital components of K and the positive hyperfine coupling constant were
estimated. The onset temperature of superconducting transition in the Knight
shift does not change so much in an applied magnetic field up to 7 T, which is
consistent with the reported high upper critical field Hc2. The Knight shift at
7 T shows an invariant behavior below Tc. No coherence peak just below Tc was
observed in the temperature dependence of the nuclear spin-lattice relaxation
rate 1/T1 in both cases of NMR and NQR. We conclude that the invariant behavior
of the Knight shift below Tc and unconventional behaviors of 1/T possibly
indicate the spin-triplet superconductivity with p- or f-wave symmetry.
