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The results of elastic, quasielastic, and inelastic neutron-scattering studies on polycrystalline CeM 2 Ge 2 (M=Ag, Au, and Ru) are presented. All compounds reveal long-range magnetic order at low temperatures. Ferromagnetic (M=Ru), antiferromagnetic (M=Au), and incommensurate (M=Ag) structures were detected. Using time-of-flight (TOF) techniques, the crystalline electric-field splittings were determined. With high-resolution TOF experiments the temperature and wave-vector dependence of the magnetic relaxation rate was studied

Elastic and inelastic neutron scattering studies of the Kondo lattice CeCu2Ge2 were performed. AtTN=4.1 K an incommensurate magnetic order develops with an ordering wave vectorq0=(0.28, 0.28, 0.54) and an ordered moment µs=0.74 µB. The crystalline electric field splits the 4f1-J-multiplet of the Ce ion into a ground state doublet and a quartet at 191 K. The wave function of the ground state yields an ordered moment of 1.54µB. Thus, due to the onset of the formation of a Kondo singlet the magnetic moment is considerably reduced. The magnetic relaxation rate Λ was investigated via quasielastic neutron scattering. The temperature dependence of Λ(T) is characteristic of heavy-fermion systems with a high temperature square root dependence and a limiting low temperature value, yielding a Kondo temperatureTK≈10K. The quasielastic component of the scattered neutron intensities persists down to the lowest temperatures, well belowTN. This quasielastic line is regarded as a characteristic feature of heavy-fermion systems and corresponds to the enhanced value of the linear term of the specific heat.

An inelastic neutron scattering study is performed on the new magnetically ordered heavy-fermion systems CeCu2Ge2 and CeAg2Ge2. The temperature dependence of the quasielastic line can be interpreted in terms of a Kondo type of behavior. In addition crystalline electric field transition energies are reported.

The crystal field splittings of the 4f-states in Er(Tl 1- c Pb c ) 3 and Pr(Tl 1- c Pb c ) 3 (cubic, Cu 3 Au-structure) have been investigated by inelastic neutron scattering. The crystal fields are cubic for all mixing ratios c . The crystal field parameters vary linearly with c . The results demonstrate the failure of the point charge model and emphasize the role played by the ligands.

The spin relaxation rates Γ in magnetically ordered Kondo lattices have been determined using neutron scattering techniques. Enhanced values of Γ and distinct deviations from a Korringa-type of relaxation behaviour were found. Gaussian contributions to the quasielastic scattered intensities were interpreted as being due to magnetic fluctuations.

Specific heat, resistivity and inelastic neutron scattering experiments are reported, which demonstrate that CeNi 2 Ge 2 exhibits a heavy-fermion groundstate which is neither magnetic nor superconducting. The specific heat coefficient γ( T ) reaches 350 mJ/K 2 mol and exhibits a peak at 0.4 K showing that coherence effects become important at low temperatures. The magnetic relaxation rates as measured via the line width in inelastic neutron scattering experiments are strongly enhanced and deviate from a Korringa law behaviour. The Kondo temperature T K ≈ 30 K was determined from the magnetic relaxation rates and from the specific heat data.