A valency change in YbCu5-xAlx from nu approximate to 2.2(x=0) to nu=3(x=2)
causes a magnetic instability near a critical concentration x(cr)approxima
te to 1.5 Alloys in the vicinity of x(cr) exhibit typical non-Fermi-liquid
properties like a negative logarithmic contribution to the specific heat or
substantial deviations of the electrical resistivity from a T-2 behavior.
Both pressure and alloying in this series bring about a strong reduction of
the Kondo temperature T-K; the crystal-held interaction and the interatomi
c exchange gain therefore importance and magnetic order becomes possible be
yond x(cr).