(Formula presented) undergoes a first-order isostructural valence transition near 40 K, whereas (Formula presented) is a moderately heavy (γ=250 mJ/mol (Formula presented)) mixed-valence compound. We have succeeded in growing single crystals of these compounds, as well as many intermediate alloys, using flux-growth techniques. The evolution from (Formula presented) to (Formula presented) has been characterized using electrical resistivity, magnetic susceptibility, and x-ray powder diffraction. The data are interpreted in terms of the evolution of the single-impurity Kondo temperature as a function of Ag concentration. © 1996 The American Physical Society.