  We address the nature of the ligandal disorder leading to local
redistributions of Kondo temperatures, manifested as annealing-induced changes
in the transport behavior of the heavy fermion system YbNi2B2C. The anomalous
transport behavior was fully characterized by temperature dependent resistivity
measurements in an extended range of 0.4 < T < 1000 K for as-grown and
optimally annealed single crystals, and microstructural changes between these
two types of samples were investigated by single-crystal x-ray diffraction and
transmission electron microscopy. Our results point to lattice dislocations as
the most likely candidate to be affecting the surrounding Yb ions, leading to a
distribution of Kondo temperatures. This effect combined with the ability to
control defect density with annealing offers the possibility of further
understanding of the more general problem of the enhanced sensitivity of
hybridized Kondo states to disorder, particularly above the coherence
temperature.
