On (α,β)-metrics with isotropic Berwald curvature

In this paper, we study almost regular (α,β)-metrics with isotropic Berwald curvature. It is surprise that such metrics must be Randers type or Berwald metric. Thus there are no non-trivial (α,β)-metrics of isotropic Berwald curvature except for Randers metrics. Further, we also classify Kropina metric which is singular with isotropic Berwald curvature.