  While the layered 122 iron arsenide superconductors are highly anisotropic,
unconventional, and exhibit several forms of electronic orders that coexist or
compete with superconductivity in different regions of their phase diagrams, we
find in the absence of iron in the structure that the superconducting
characteristics of the end member BaPd2As2 are surprisingly conventional. Here
we report on complementary measurements of specific heat, magnetic
susceptibility, resistivity measurements, Andreev spectroscopy, and synchrotron
high pressure x-ray diffraction measurements supplemented with theoretical
calculations for BaPd2As2. Its superconducting properties are completely
isotropic as demonstrated by the critical fields, which do not depend on the
direction of the applied field. Under the application of high pressure, Tc is
linearly suppressed, which is the typical behavior of classical phonon-mediated
superconductors with some additional effect of a pressure-induced decrease in
the electronic density of states and the electron-phonon coupling parameters.
Structural changes in the layered BaPd2As2 have been studied by means of
angle-dispersive diffraction in a diamond-anvil cell. At 12 GPa and 24.2 GPa we
observed pressure induced lattice distortions manifesting as the discontinuity
and, hence discontinuity in the Birch-Murnaghan equation of state. The bulk
modulus is B0=40(6) GPa below 12 GPa and B0=142(3) GPa below 27.2 GPa.
