Direct observation of domains in the low temperature phase of p-terphenyl

For the first time ferroelastic domains are observed in the low temperature phase of p-terphenyl. These domains are only distinguishable in very thin crystals of a few micrometers. Plane boundaries are found perpendicular to the two-fold axis. Birefringence measurements are compatible with the order parameter temperature dependence as determined by superstructure intensities.