Rare earth metals have distinct influence on hydrogenation,magnetic and catalytic properties of the Pd-rich alloys.Investigation on the most Pd-rich compounds in the Pd-RE systems is significant.In this work,single phase compounds CePd5,PrPd5 and NdPd5 were prepared by a proper smelting and heat treatment.X-ray diffraction was used to determine their structure and lattice parameters.It is found that the most Pd-rich compound in the Pd-Ce system is CePd5 with the hexagonal CaCu5-type structure,and that in the Pd-Pr and Pd-Nd system is PrPd5 and NdPd5 with the orthorhombic SmPt5-type structure,respectively.X-ray diffraction data for the three intermetallic compounds have been reported.Following lattice parameters have been obtained:a=0.5372 nm,c=0.4178 nm for CePd5;a=0.5278 nm,b=0.9239 nm,c=2.575 nm for PrPd5;a=0.5265 nm,b=0.9219 nm,c=2.570 nm for NdPd5.The stoichiometries and the crystal structures of the most Pd-rich compounds in the Pd-RE systems have been compared with those in the Pt-RE systems.