  Very high applied pressure induces superconductivity with the transition
temperature ($T_c$) exceeding 19 K in elemental yttrium, but relatively little
is known about the nature of that superconductivity. From point-contact
spectroscopy (PCS) measurements in a diamond anvil cell (DAC), a strong
enhancement in the differential conductance is revealed near the zero-biased
voltage owing to Andreev reflection, a hallmark of the superconducting (SC)
phase. Analysis of the PCS spectra based on the extended
Blonder-Tinkham-Klapwijk (BTK) model indicates two SC gaps at 48.6 GPa, where
the large gap $\Delta_L$ is 3.63 meV and the small gap $\Delta_S$ is 0.46 meV.
When scaled against a reduced temperature, both small and large SC gaps
collapse on a single curve that follows the prediction from BCS theory. The SC
gap-to-$T_c$ ratio is 8.2 for the larger gap, and the initial slope of the
upper critical field is -1.9 T/K, indicating that Y belongs to a family of
strongly coupled BCS superconductors. The successful application of PCS to Y in
DAC environments demonstrates its utility for future research on other
pressure-induced high-$T_c$ superconductors.
