The magnetic susceptibility of the intermetallic compounds RInCu4 (R = Gd, Er and Yb) was measured under helium gas pressure up to 2 kbar at the fixed temperatures 78, 150 and 300 K. For YbInCu4, which exhibits a first-order valence phase transition at TV40 K, the Grüneisen parameter for the Kondo energy, K-dlnTK/dlnV = -32, is large and typical for Ce-based heavy-fermion systems in magnitude but opposite in sign. The effect of atomic disorder is discussed on the basis of the data for a chemically disordered sample; the pressure effect at T = 78 K is strongly enhanced due to the spatial dispersion of pressure-sensitive TV, and hence dTV/dP = -2.0 K kbar-1 is obtained by assuming a Gaussian distribution of TV. On the basis of an extrapolation of the experimental pressure dependence, a (P,T) phase diagram is proposed for YbInCu4. Reference compounds with stable f moments, GdInCu4 and ErInCu4, show negligible pressure dependences of the susceptibility.

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