  Despite the fact that GeTe is known to be a very interesting material for
applications in thermoelectrics and for phase-change memories, the knowledge on
its low-temperature transport properties is only limited. Here, we report on
phase-coherent phenomena in the magnetotransport of GeTe nanowires. From
universal conductance fluctuations, a phase-coherence length of about 200nm at
0.5K is determined for the hole carriers. The distinct phase-coherence is
confirmed by the observation of Aharonov--Bohm type oscillations for magnetic
fields applied along the nanowire axis. We interpret the occurrence of these
magnetic flux-periodic oscillations by the formation of a tubular hole
accumulation layer on the nanowire surface. In addition, for
Nb/GeTe-nanowire/Nb Josephson junctions, we obtained a proximity-induced
critical current of about 0.2$\mu$A at 0.4K. By applying a magnetic field
perpendicular to the nanowire axis, the critical current decreases monotonously
with increasing magnetic field, which indicates that the structure is in the
small-junction-limit. Whereas, by applying a parallel magnetic field the
critical current oscillates with a period of the magnetic flux quantum
indicating once again the presence of a tubular hole channel.
