Generalized twisted Gabidulin codes

Let C be a set of m by n matrices over Fq such that the rank of A−B is at least d for all distinct A,B∈C. Suppose that m⩽n. If #C=qn(m−d+1), then C is a maximum rank distance (MRD for short) code. Until 2016, there were only two known constructions of MRD codes for arbitrary 1