Non-Fermi-liquid effects at ambient pressure in the stoichiometric heavy-fermion compound YbRh2Si2

Strong deviations from the properties of a heavy Landau Fermi-liquid alread y at ambient pressure and zero held are reported for single-crystalline YbR h2Si2. The low-temperature specific-heat coefficient and the electrical res istivity show a logarithmic and a linear temperature dependence, respective ly, in more than a decade in temperature. This anomalous metallic state is ascribed to the proximity of a very nearby magnetic instability. Applicatio n of hydrostatic pressure induces anomalies in the electrical resistivity, indicating the onset of long-range magnetic order at a critical pressure p( c) similar or equal to 0.5 GPa, which is so far the lowest required for the onset of magnetism in Yb compounds. (C) 2000 Elsevier Science B.V. All rig hts reserved.