  We establish a sharp large deviation principle for renewal-reward processes,
supposing that each renewal involves a broad-sense reward taking values in a
real separable Banach space. In fact, we demonstrate a weak large deviation
principle without assuming any exponential moment condition on the law of
waiting times and rewards by resorting to a sharp version of Cram\'er's
theorem. We also exhibit sufficient conditions for exponential tightness of
renewal-reward processes, which leads to a full large deviation principle.
