Relative braid group symmetries on quantum supersymmetric pairs of type sAIII

We introduce the relative Coxeter groupoid and construct intrinsic relative braid group symmetries for quantum supersymmetric pairs of type sAIII. These symmetries are constructed by establishing new intertwining properties of quasi $K$-matrices, which generalize the earlier non-super construction of Wang and the second author. We derive explicit formulas for these symmetries and prove that they satisfy the braid relations in the relative Coxeter groupoid.