The results of an on-going study of Yblnl _ ~AgxCu4 are presented. YblnCu4 undergoes a first-order valence transition at 40 K, while YbAgCu4 is an isostructural heavy Fermion compound. We have succeeded in growing single crystals of these compounds, as well as intermediate alloys, using flux-growth techniques. A smooth evolution from YblnCu4 to YbAgCu4 is observed. Results on the influence of sample quality, as well as the effect of other dopants, on the valence transition in YblnCu4 are also discussed.

We present transport and thermodynamic measurements as a function of temperature ͑0.1-300 K͒, pressure ͑1 bar-16 kbars͒, and magnetic field ͑0-600 kOe͒ on YbInNi 4. Ferromagnetism arises near 3 K out of a state with enhanced electronic specific-heat coefficient. Resistivity, specific-heat, and magnetization measurements imply that the ground state of YbInNi 4 is a crystal-field doublet, whereas earlier neutron-scattering results suggest a ground-state quartet. We also compare YbInNi 4 to YbInCu 4 and intermediate alloys. ͓S0163-1829͑98͒00613-4͔