An Ottawa-based pension fund that invests on behalf of the Royal Canadian Mounted Police and Canadian Armed Forces is Newton-based WS Development’s financial partner on the next phase of Boston’s Seaport Square development.

WS revealed the partnership with PSP Investments in announcing Amazon’s lease of a 430,000-square-foot office building off Congress and Summer Streets. Amazon will expand by 2,000 employees in the Seaport for its cloud computing, voice recognition, machine learning and robotics research. The new building is scheduled for completion in 2021, doubling Amazon’s Greater Boston workforce.

PSP Investments had nearly $140 billion under management as of Sept. 30, including a $20.6-billion real estate portfolio as of March 2017. Office properties are its largest allocation at 29.2 percent, while residential and retirement properties make up another 29.1 percent of its portfolio which returned 10.8 percent in 2018.

International pension funds have made some of the highest-ticket investments in Boston real estate in recent years.

Toronto-based Oxford Property Group is one of the city’s largest commercial landlords after acquiring five trophy office towers in Boston and Cambridge from Blackstone Group for $2.1 billion in 2014.

And Australian pension fund AustralianSuper partnered with Brookfield Property Partners on the 2015 acquisition of 75 State St.