  The ternary semiconductor AgInTe$_2$ is a thermoelectric material with
chalcopyrite-type structure that transforms reversibly into a rocksalt-type
structure under high pressure. Nuclear magnetic resonance (NMR) is considered
to provide unique insight into material properties on interatomic length
scales, especially in the context of structural phase transitions. Here,
$^{115}$In and $^{125}$Te NMR is used to study AgInTe$_2$ for ambient
conditions and pressures up to 5 GPa. Magnetic field dependent and magic angle
spinning (MAS) experiments of $^{125}$Te prove strongly enhanced internuclear
couplings, as well as a distribution of isotropic chemical shifts suggesting a
certain degree of cation disorder. The indirect nuclear coupling is smaller for
$^{115}$In, as well as the chemical shift distribution in agreement with the
crystal structure. The $^{115}$In NMR is further governed by a small
quadrupolar interaction ($\nu_\mathrm{Q} \approx$ 90 kHz) and shows an orders
of magnitude faster nuclear relaxation in comparison to that of $^{125}$Te. At
a pressure of about 3 GPa, the $^{115}$In quadrupole interaction increases
sharply to about 2400 kHz, indicating a phase transition to a structure with a
well defined, though non-cubic local symmetry, while the $^{115}$In shift
suggests no significant changes of the electronic structure. The NMR signal is
lost above about 5 GPa (at least up to about 10 GPa). However, upon releasing
the pressure a signal is recovered that points to the reported metastable
ambient pressure phase with a high degree of disorder.
