31P Nuclear Magnetic Resonance of Charge-Density-Wave Transition in a Single Crystal of RuP*

We perform 31P nuclear magnetic resonance (NMR) measurements on a single crystal of RuP. The anomalies in resistivity at about TA = 270 K and TB = 330 K indicate that two phase transitions occur. The line shape of 31P NMR spectra in different temperature ranges is attributed to the charge density distribution. The Knight shift and spin-lattice relaxation rate 1/T1T are measured from 10 K to 300 K. At about TA = 270 K, they both decrease abruptly with the temperature reduction, which reveals the gap-opening behavior. Well below TA, they act like the case of normal metal. Charge-density-wave phase transition is proposed to interpret the transition occurring at about TA.