We address the long-standing mystery of the nonmagnetic insulating state of the intermediate valence compound SmB6. Within a combination of the local density approximation (LDA) and an exact diagonalization (ED) of an effective discrete Anderson impurity model, the intermediate valence ground state with the f-shell occupation <n(4f)> = 5.6 is found for the Sm atom in SmB6. This ground state is a singlet, and the first excited triplet state similar to 3 meV higher in the energy. SmB6 is a narrow band insulator already in LDA, with the direct band gap of similar to 10 meV. The electron correlations increase the band gap which now becomes indirect. Thus, the many-body effects are relevant to form the indirect band gap, crucial for the idea of ``topological Kondo insulator{''} in SmB6. Also, an actinide analog PuB6 is considered, and the intermediate valence singlet ground state is found for the Pu atom. We propose that {[} Sm, Pu]B-6 belong to a new class of the intermediate valence materials with the multi-orbital ``Kondo-like{''} singlet ground-state. Crucial role of complex spin-orbital f(n)-f(n+1) multiplet structure differently hybridized with ligand states in such Racah materials is discussed.