FCLoopRemoveNegativePropagatorPowers[exp]
rewrites propagators raised to integer powers as products.
[{q, m, -1}]
SFAD
= FCLoopRemoveNegativePropagatorPowers[%] ex
// StandardForm
ex
(*-m + Pair[Momentum[q, D], Momentum[q, D]]*)
[{q, m}, q + p, {q, m, -2}]
SFAD
= FCLoopRemoveNegativePropagatorPowers[%] ex
// StandardForm
ex
(*FeynAmpDenominator[StandardPropagatorDenominator[Momentum[p, D] + Momentum[q, D], 0, 0, {1, 1}]] (-m + Pair[Momentum[q, D], Momentum[q, D]])*)