The newly completed six-story building that is the first phase of the Research Boulevard Center in Rockville now has Geomet Inc., a government contractor, as a tenant taking 40,000 square feet and Tracor Inc. leasing 20,000 square feet.

Both contracts were arranged by Julien J. Studley Inc., agent for the 280,000-square-foot structure.

Porten-Bloom Associates is constructing 33,000 square feet of condominium office space at 4400 MacArthur Blvd., north of Georgetown.Designed to resemble red brick town houses, the project will have 75 parking spaces. Swaney-Kerns did the architectural plans.

The Braedon Companies arranged the lease of 40,000 square feet for International City Management Association to become the first tenant in a new building at 1120 G. St. NW. The ICMA is a professional and educational organization that will use four floors of the building to be completed in 1982 by Bender Associates.

H. G. Smithy Co. announced that the 175,000 square feet in the former Marriott headquarters building on River Road in Bethesda have been fully leased and occupied under the direction of Paul Grinberg Jr. The six buildings, now owned by a limited partnership, were the subject of a $500,000 rehabilitation. Tenancies include a cafeteria, office and warehouse users and a tennis facility.

Squire, Sanders & Dempsey, one of the nation's largest law firms, has signed a long-term lease for 69,000 square feet in a building being constructed at 1201 Pennsylvania Ave. NW. The lease for the building being developed by Cabot, Cabot & Forbes of Boston was arranged by the Washington office of Julien J. Studley Inc. Occupancy is scheduled for the fall of 1981.

Shannon & Luchs arranged for leasing more than 16,700 square feet of space in the GT building at Dulles Airport. Mitel Corp. is the tenant.

The Carey Winston Co. arranged for Delon Hampton & Associates, a civil engineering firm, to lease 15,776 square feet in a a new office building at Montrose Road and I-270 in Rockville. Occupancy begins this month.