  We theoretically propose a mechanism to understand the violation of the
Pauli-Clogston limit for the upper critical field H$_{\rm c2}$ observed in the
Ce bearing heavy Fermion material CeRh$_2$As$_2$ from the view point of spin
singlet pairing. It is based on a duality concept, the dual simultaneous
aspects of an electron: the itinerant part and localized part of
quasi-particles (QPs) originated from the 4f electrons of the Ce atoms. While
the itinerant QPs directly participate in forming the Cooper pairs, the
localized QPs exert the internal field so as to oppose the applied field
through the antiferromagnetic exchange interaction between them. This is
inherent in the dense Kondo lattice system in general. We argue that this
mechanism can be applied not only to the locally noncentrosymmetric material
CeRh$_2$As$_2$, but also to globally inversion symmetry broken Ce-based
materials such as CePt$_3$Si. Moreover, we point out that it also works for
strongly Pauli limit violated spin triplet pairing systems, such as UTe$_2$.
