We have measured the differential resistance of point-contacts between Pt and the MeBe13-compounds with Me = La,Ce,Yb and U as function of bias U. The characteristics of Ce- and YbBe13 show an asymmetry which is typical for an f-instability, and so does UBe13. © 1987.

We have studied CeCu6 by inelastic neutron scattering. We found both quasielastic and also inelastic transitions, which we interpret as residual crystal field transitions. The quasielastic linewidth is a strongly nonlinear function of temperature, with approximately ΓQE=5.0 meV at 300 K, with a crossover ΓQE=kT at about 13 K and with a residual value of ΓQE=(0)=0.50 meV for T=0 K. Below 5 K the quasielastic intensity IQE decreases linearly with temperature. χstαIQE/T is in good agreement with direct measurements of the static susceptibility. The data are fully consistent with a nonordering groundstate of CeCu6. © 1986 Springer-Verlag.

We have measured the current-voltage characteristics of point contacts between UBe13 or UPt3 and the normal metals W or Pt (metallic point contacts) or GaAs (Schottky-barrier tunneling contact) in the temperature range between 50 mK and 1 K. In the metal-point-contact characteristics (dVdI vs V) there appear zero-bias minima of width 2 below Tc. The ratio 2 kBTc is close to the BCS value. The tunneling spectra of UPt3 exhibit weak additional structure below Tc. A value 2 has been estimated, which is a factor of 2 larger than that for the metal point contacts. © 1987 The American Physical Society.

We present results of single crystal neutron diffraction experiments on La2-xSrxCuO4-δ. The analysis of the temperature dependence of the LaO bond lengths shows that almost the entire thermal contraction of La2CuO4 between 540 K an 50 K is due to the decrease of the LaO9 polyhedron, the CuO bond distances remain almost constant. Doping of La2CuO4 with Sr (or additional O) decreases both CuO bond lengths. The large thermal parameters especially of the apical O indicate the instability of all examined crystals against a second phase transition. © 1991.