Each state employee who is a member of the state employees retirement system, part A, may, upon the enactment of and pursuant to federal-enabling legislation, elect to be covered by Social Security and, from the date of such election, he shall pay his required Social Security contribution. If the federal-enabling legislation shall allow such employee to be covered by Social Security retroactively, then, upon payment to the state employees retirement system by such employee of the amount required to be paid by him as an employee, the state shall take all the necessary steps and make all the necessary payments to the federal government to effectuate such Social Security coverage. The payment for retroactive coverage may be made in accordance with a payment schedule, without interest, as may be established by the State Employees Retirement Commission. Upon payment of all necessary contributions by such employee, upon retirement he shall be entitled to receive, in addition to any Social Security benefits, his full retirement salary as a member of part A of the state employees retirement system.