  We present temperature-dependent magneto-transport measurements on as-grown
and annealed YbNi$_2$B$_2$C single crystals. Annealing causes drastic changes
in the Hall coefficient, $R_H(T)$. Whereas for as-grown samples the Hall
coefficient is negative between room temperature and 2 K, with a pronounced
{\it minimum} at $\approx 22$ K, for the samples annealed at $950^\circ$ C for
150 hours, $R_H(T)$ changes its sign twice in the same temperature range: from
negative to positive on cooling below $\sim 100$ K and back to negative below
$\sim 10$ K, and has a clear {\it maximum} at $\approx 45$ K. Intermediate
temperature dependencies can be achieved by reducing the annealing time. These
findings are discussed within the framework of an annealing dependence of the
skew scattering in conjunction with the recent structural, thermodynamic and
transport studies of the effects of annealing in YbNi$_2$B$_2$C.
