(a)Definitions. Part-time career employment means regularly scheduled work of from 16 to 32 hours per week performed by an employee of an agency as defined in 5 U.S.C. 3401(a) through (f) , who has an appointment in tenure group I or II and who becomes employed on such part-time basis on or after April 8, 1979. Tenure group I applies to employees in the competitive service under career appointments who are not serving probation and permanent employees in the excepted service whose appointments carry