Eps[a, b, c, d] is the head of the totally antisymmetric (Levi-Civita) tensor. The a,b, ... may have head LorentzIndex, Momentum or Integer. In case of integers the Levi-Civita tensor is evaluated immediately.
See also: EpsEvaluate, LC, LCD, LeviCivita.
The FeynCalc Book | DotSimplify | EpsChisholm |