Magnetic properties of the Kondo metals CePtSn and CePdSn from mu SR

While the transition into the antiferromagnetic state in CePdSn proves to be of simple second order, the transition in CePtSn is of an unusual nature. About 1 K above T-N the Ce moments enter a quasi-static state with the paramagnetic spins frozen at random orientations. In the antiferromagnetic states, well-developed sharp spin precession patterns are seen in both compounds. This feature is not easily reconciled with the incommensurate spin structures proposed by neutron diffraction measurements. Implications on spin structure resulting from the mu SR data are discussed.