Superconductivity and magnetism in noncentrosymmetric LaPtGe3 and CePtGe3

LaPtGe3 and CePtGe3 crystallize with a noncentrosymmetric body-centered tetragonal (space group I4mm) BaNiSn3 type of structure. LaPtGe3 is a weakly coupled BCS-like s-wave type-I superconductor with Tc = 0:55 K, Bc ' 14 mT and Ginzburg-Landau parameter kGL = 0:044 < 1= p 2, which is obtained from the free electron model. CePtGe3 is a Curie-Weiss paramagnet with an effective magnetic moment mueff = 2:46 muB. The Ce moments show two antiferromagnetic ordering transitions at TN1 ~ 3:7 K and TN2 ~ 2:7 K and a ground state multiplet J = 5=2 splitting into three doublets (splitting energies from the ground state d1 = 46 K and d2 = 137 K). The reduced magnetic entropy at TN1 together with an enhanced Sommerfeld coeffcient suggest that the magnetic orderings in CePtGe3 originates from dominating RKKY interactions.