employ experts and consultants in accordance with
section 3109 of title 5, and compensate individuals so employed for each day (including travel time) at rates not in excess of the maximum rate of basic pay for grade GS–15 as provided in section 5332 of such title, and while such experts and consultants are so serving away from their homes or regular place of business, to pay such employees travel expenses and per diem in lieu of subsistence at rates authorized by section 5703 of such title 5 for persons in Federal Government service employed intermittently;