  We present the first scanning tunneling spectroscopy study on the Chevrel
phase PbMo6S8, an extreme type II superconductor with a coherence length only
slightly larger than in high-Tc cuprates. Tunneling spectra measured on
atomically flat terraces are spatially homogeneous and show well-defined
coherence peaks. The low-energy spectral weight, the zero bias conductance and
the temperature dependence of the gap are incompatible with a conventional
isotropic s-wave interpretation, revealing the presence of low-energy
excitations in the superconducting state. We show that our data are consistent
with the presence of nodes in the superconducting gap.
