5 USC 5336 - Additional step-increases

(a) Within the limit of available appropriations and under regulations prescribed by the Office of Personnel Management, the head of each agency may grant additional step-increases in recognition of high quality performance above that ordinarily found in the type of position concerned. However, an employee is eligible under this section for only one additional step-increase within any 52-week period.
(b) A step-increase under this section is in addition to those under section 5335 of this title and is not an equivalent increase in pay within the meaning of section 5335 (a) of this title.
(c) This section does not apply to the pay of an individual appointed by the President, by and with the advice and consent of the Senate.