  We apply near-field matter-wave interferometry to determine the absolute
scalar polarizability of the fullerenes C$_{60}$ and C$_{70}$. A key feature of
our experiment is the combination of good transmission and high spatial
resolution, gained by wide molecular beams passing through sub-micron gratings.
This allows to significantly facilitate the observation of field-dependent beam
shifts. We thus measure the polarizability to be $\alpha=88.9 \pm 0.9 \pm 5.1
  \rm \AA^{3}$ for C$_{60}$ and to $\alpha = 108.5 \pm 2.0 \pm 6.2 \rm \AA^{3}$
for C$_{70}$.
