  Remarkable nonlinearities in the differential tunneling conductance between
fractional quantum Hall edge states at a constriction are observed in the
weak-backscattering regime. In the $\nu $ = 1/3 state a peak develops as
temperature is increased and its width is determined by the fractional charge.
In the range $2/3 \le \nu \le 1/3$ this width displays a symmetric behavior
around $\nu $ = 1/2. We discuss the consistency of these results with available
theoretical predictions for inter-edge quasiparticle tunneling in the
weak-backscattering regime.
