Chevalley supergroups of type D(2,1;a)

We present a construction “a` la Chevalley” of connected affine supergroups associated with Lie superalgebras of type D(2,1;a), for any possible value of the parameter a. This extends the results in [R. Fioresi, F. Gavarini, Chevalley Supergroups, Memoirs AMS 215 (2012), no. 1014] (and [R. Fioresi, F. Gavarini, On the construction of Chevalley supergroups, Supersymmetry in Mathematics & Physics (UCLA Los Angeles, U.S.A. 2010), 101–123, Lecture Notes in Mathematics 2027, Springer-Verlag, Berlin-Heidelberg, 2011]) where all other simple Lie superalgebras of classical type were considered. The case of simple Lie superalgebras of Cartan type being dealt with in [F. Gavarini, Algebraic supergroups of Cartan type, Forum Mathematicum (to appear), 92 pages], so this work completes the program of constructing connected affine supergroups associated with any simple Lie superalgebra.