Non-Fermi-liquid behaviour of U3-xNi3Sn4-y single crystals

U3Ni3Sn4 and U2.9Ni3.0Sn3.9 single crystals exhibit a non-Fermi-liquid susceptibility chi proportional to T-0.3 between 1.7 and 10 K. The electronic heat capacity coefficient gamma(T) of U2.9Ni3.0Sn3.9 varies as the square root of temperature between 0.3 and 5 K. Although most available non-Fermi-liquid models are in disagreement with these results, the heat capacity data are consistent with a renormalization group calculation for magnetic fluctuations near an antiferromagnetic quantum critical point (QCP). Alternatively, both the magnetic and heat capacity data can be fitted to a Griffiths-phase model for magnetic clusters near a QCP, using a single characteristic exponent lambda = 0.7.