Citizens Bank is downsizing its office space north of Boston with the sale and partial leaseback of a Medford property near the Orange Line while seeking tenants for the remaining 31,290 square feet.

National Development and Charles River Realty Investors acquired 20 Cabot Road for $31.7 million last week. Citizens leased back 85,200 square feet on three floors.

The fourth floor is available for lease, with spaces subdividable to as small as 6,000 square feet. Cushman & Wakefield represents ownership in leasing.

Completed in 1987, the building is situated on 8.3 acres. National Development, which will manage the property, plans a capital improvement program including updated lobby and common areas and a new fitness center.

Cambridge Savings Bank provided $26.05 million in mortgage financing for the March 28 transaction.

Like other office buildings in the neighborhood near the Medford-Everett line, the property is positioned as a less expensive alternative to Boston and Cambridge, with nearby public transit at Wellington station on the MBTA Orange Line. Asking rents are in the mid- to upper-$30 per square foot range on a gross basis, said Scott Gredler, a senior director at Cushman & Wakefield.

In its first local office expansion outside Boston and Cambridge, Amazon recently agreed to lease 50,000 square feet at The Davis Cos.’ One Cabot office building in Medford. The office will house 200 researchers on the Alexa voice recognition system, the Boston Globe reported.

And vehicle telematics firm Agero is scheduled to relocate this spring from One Cabot Road to a new 115,000-square-foot headquarters at 400 River’s Edge in Medford, part of Preotle Lane & Assoc.’s 1-million-square-foot master-planned development on the Malden River.