  We find discrete holomorphic parafermions of the Ashkin-Teller model on the
critical line, by mapping appropriate interfaces of the model to the $O(n=1)$
model. We give support to the conjecture that the curve created by the
insertion of parafermionic operators at two points on the boundary is
$SLE(4,\rho,\rho)$, where $\rho$ varies along the critical line.
