  The low-temperature thermal and transport properties of an unusual kind of
crystal exhibiting minimal molecular positional and tilting disorder have been
measured. The material, namely, low-dimensional, highly anisotropic
pentachloronitrobenzene (PCNB) has a layered structure of rhombohedral parallel
planes in which the molecules execute large-amplitude in-plane as well as
concurrent out-of-plane librational motions. Our study reveals that
low-temperature glassy anomalies can be found in a system with minimal disorder
due to the freezing of (mostly in-plane) reorientational jumps of molecules
between equivalent crystallographic positions with partial site occupation. Our
findings will pave the way to a deeper understanding of the origin of
above-mentioned universal glassy properties at low temperature.
