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The electronic and magnetic properties of the ternary cerium compounds Ce 2 PdGe 6 and Ce 2 PtGe 6 are reported within the context of measurements of electrical resistivity, magnetoresistivity, and magnetic susceptibility. Ce 2 PdGe 6 orders magnetically at T N = 11.5 K , and Ce 2 PtGe 6 at T N = 9.9 K . In the ordered region, the magnetization as well as the magnetoresistance reveal anomalous behaviour for both compounds, which are ascribed to metamagnetic transitions into a field-induced ferromagnetic state.

The neutron diffraction and magnetic susceptibility studies have shown that the magnetic structure of UPd 2 Ge 2 changes dramatically even under very low iron doping. Though the general magnetic structure of pure UPd 2 Ge 2 and of 1%Fe-doped samples is the same, the temperature intervals of existence of different magnetic phases are different. The values of transition temperatures, where (i) the `square’ modulated longitudinal spin-density wave (LSDW) structure with the propagation vector k =(0; 0; k z = 3 4 ) starts to transform into the sinusoidal modulated LSDW structure and (ii) the commensurate phase transforms into incommensurate one, shift under the 1%Fe doping to the higher temperatures (from 50 to 65 K and from 80 to 90 K, respectively). In the pure and 1%Fe-doped UPd 2 Ge 2 , the magnetic transition from the commensurate to incommensurate phase is accompanied by the drastic decrease of the propagation vector k z . In the 2%Fe-doped sample, besides the Neel point of T N =135 K, we have found two additional characteristic temperatures of 65 and 93 K. Below 65 K, the material has a simple antiferromagnetic (AF) structure with the propagation vector k =(0; 0; 1) and, at 65 K T T N , the magnetic structure is LSDW with sinusoidal modulation. Over almost the total region 65 K T T N , the LSDW magnetic structure is incommensurate. Only at about 93 K, the propagation vector passes the commensurate value of 3 4 , whereas k z > 3 4 at 65 T k z 3 4 at 93 K T T N . We have found that the magnetic susceptibility and the uranium magnetic moment are sensitive to the k z > 3 4 ⇒k z 3 4 transition. With increasing iron concentration to x ⩾0.15, the simple AF structure with k =(0; 0; 1) develops over all temperature region up to the Neel point. Below T N , the uranium magnetic moments are always parallel to the tetragonal c -axis.

CePt 2 Si crystallizes in the inverse CeNiSi 2 -type structure. Magnetic properties are dominated by a mutual interaction of the RKKY interaction, the Kondo effect and crystalline electric field splitting, resulting in long range magnetic order below about 7 K . A slightly enhanced Sommerfeld value γ = 42 mJ / mol K 2 and a distinct temperature dependence of the electrical resistivity refers to Kondo interaction in presence of strong crystalline electric field splitting.