  In standard quantum field theory, the one-particle states are classified by
unitary representations of the Poincar\'e group, whereas the causal fields'
classification employs the finite dimensional (non-unitary) representations of
the (homogeneous) Lorentz group. A natural question arises - why the fields are
not allowed to transform nontrivially under translations? We investigate this
issue by considering the fields that transform under the full representation of
the Poincar\'e group. It follows that such fields can be consistently
constructed, although the Lagrangians that describe them necessarily exhibit
explicit dependence on the space-time coordinates. The two examples of the
Poincar\'e-spinor and the Poincar\'e-vector fields are considered in details.
The inclusion of Yang--Mills type interactions is considered on the simplest
example of the U(1) gauge theory. The generalization to the non-abelian case is
straightforward so long as the action of the gauge group on fields is
independent of the action of the Poincar\'e group. This is the case for all the
known interactions but gravity.
