  We report on measurements of the anisotropic dynamical polarizability of Dy
near the 626-nm intercombination line, employing modulation spectroscopy in a
one-dimensional optical lattice. To eliminate large systematic uncertainties
resulting from the limited knowledge of the spatial intensity distribution, we
use K as a reference species with accurately known polarizability. This method
can be applied independently of the sign of the polarizability, i.e. for both
attractive and repulsive optical fields on both sides of a resonance. By
variation of the laser polarization we extract the scalar and the tensorial
part. To characterize the strength of the transition, we also derive the
natural linewidth. We find our result in excellent agreement with literature
values, which provide a sensitive benchmark for the accuracy of our method. In
addition we demonstrate optical dipole trapping on the intercombination line,
confirming the expected long lifetimes and low heating rates. This provides an
additional tool to tailor optical potentials for Dy atoms and for the
species-specific manipulation of atoms in the Dy-K mixture.
