FCLoopBasisCreateScalarProducts {q1, q2, ...}, {p1, p2, ...}, {d1, d2, ...}, head] generates a list of all loop-momentum dependent scalar products made out of the loop momenta q1, q2, ... and external momenta p1, p2, ... in the space-time dimensions d1, d2, .... The argument head can be Pair to generate Lorentzian scalar products or CartesianPair to generate Cartesian scalar products.
FCLoopBasisCreateScalarProducts[{l}, {}, {D}, Pair]\left\{l^2\right\}
FCLoopBasisCreateScalarProducts[{l}, {p1, p2}, {4}, Pair]\left\{\overline{l}^2,\overline{l}\cdot \overline{\text{p1}},\overline{l}\cdot \overline{\text{p2}}\right\}
FCLoopBasisCreateScalarProducts[{l}, {}, {D - 1}, CartesianPair]\left\{l^2\right\}