“…Existence of first integrals is of great importance, they provide a lot of information about the corresponding geometry, including some rigidity results, [6], [7], [21] In Riemannian geometry, Topalov and Matveev obtained in [21], for two projectively equivalent metrics on an n-dimensional manifold, a set of n first integrals. An extension of this result to the Finslerian context has been proposed by Sarlet in [16]. In [7], Foulon and Ruggiero have shown the existence of a first integral for k-basic (of isotropic curvature) Finsler surfaces.…”