All science is materialistic

[Jehanne]

As you and everyone else knows, by Einstein's very famous formula,


one has the mass–energy equivalence, and so, massless particles, such as photons, would have zero invariant mass.  Materialism would certainly encompass the notion of fields (of course, the basis of QFT), where at very high energies a field would produce a particle (e.g., the Higgs boson).

Matter and mass are not equivalent terms.

Energy would be in Joules, mass would be in kilograms and '"c squared' would be meters squared divided by seconds squared.