YbNiB(4): a Kondo lattice with low-dimensional antiferromagnetic fluctuations.

We have grown single crystals of YbNiB(4) using a Ni(60)B(40) flux and determined the magnetic properties of this compound by means of magnetic susceptibility, specific heat and electrical resistivity measurement. Yb ions in YbNiB(4) are in a trivalent state and present a transition from a paramagnetic state to an antiferromagnetic (AF) state at T(N1) = 5.4 K and a further transition towards a second AF state at T(N2) = 4.0 K. Kondo type behavior in the resistivity and an enhanced Sommerfeld coefficient γ = 100 mJ mol(-1) K(-2) provide evidence for a significant Kondo interaction. A broad maximum in χ(T) at around 8 K, well above T(N1), suggests low-dimensional antiferromagnetic correlations. Both mechanisms lead to strong fluctuation in an extended temperature range above T(N1), up to the characteristic energy of this system, which was estimated to be T(4f) = 16 K from an analysis of the entropy.