Suppression of magnetic order in YbNiSi3 by magnetic fields

The heavy-fermion compound YbNiSi3 orders antiferromagnetically below the Neel temperature TN=5.1K. The magnetic order can be suppressed either by applying a magnetic field of Bc=8.3T(for B parallel b) or by replacing Si with Ge. The latter is equivalent to a negative lattice pressure. In search of a field-induced quantum phase transition, we studied the disappearance of magnetic order in YbNiSi3 at Bc, using specific-heat and resistivity measurements. Apart from a slightly enhanced specific heat and resistivity at Bc, no signs for quantum criticality could be identified down to 0.35K. Our data indicate that YbNiSi3 belongs to the heavy-fermion compounds in which the magnetic field gradually reduces the amount of antiferromagnetic order until the magnetic entropy vanishes continuously at Bc and the system changes smoothly to a field-polarized paramagnet