Dimethyl terephthalate is a basic material for the technical production of polyesters, for example polyethylene terephthalate (PET) or polybutylene terephthalate (PBT). It is also used in the production of polyester resins for films, lacquers and adhesives and of 1,4-dimethylolcyclohexane. The abbreviation for dimethyl terephthalate is DMT, it is possible that there is confusion here with Dimethyltryptamine whose abbreviation is also DMT.
If you want to be sure that your amphetamine really only contains amphetamine and in what dose, you should have it chemically analysed.