  A genus one curve C of degree 5 is defined by the 4 x 4 Pfaffians of a 5 x 5
alternating matrix of linear forms on P^4. We prove a result characterising the
covariants for these models in terms of their restrictions to the family of
curves parametrised by the modular curve X(5). We then construct covariants
describing the covering map of degree 25 from C to its Jacobian and give a
practical algorithm for evaluating them.
