endorsement by the National Institute of Standards and Technology (NIST), nor does it imply that the products identified are necessarily the best available for the purpose. Nanocalorimeter fabrication was performed in part at the NIST Center for Nanoscale Science & Technology (CNST). optical functions of CuP 2 were represented by a Kramers-Kronig-consistent b-spline function with 0.1 nodes/eV. Ellipsometry spectra were fitted with the CompleteEase software (J.A. Woollam).