Minimal tori in R⁴

We describe tools for the study of minimal surfaces in R⁴; some are classical (the Gauss maps) and some are newer (the link/braid/writhe at infinity). Then we look for complete proper non holomorphic minimal tori with total curvature $-8π$ and a single end immersed in R⁴. We translate the problem into a system of $10$ quadratic or linear equations in $11$ real variables with coefficients in terms of the Weierstrass function and give explicit solutions for these equations if T is a rectangular torus. For the square torus, we have a complete answer with a unique family of solutions generalizing the Chen-Gackstetter torus in R³. On the other hand, we show that there is no solution on the equianharmonic torus.