The city last conducted a similar search for its retirement plans in 2017.
The plan is in the process of identifying a replacement manager for the roughly $80 million mandate.
Northwestern Mutual will acquire a minority equity interest in Sixth Street.
The plan’s current general manager will retire at the end of this quarter.
The plan also placed two investment managers on watch last month.
The pension plan hired a domestic core fixed-income manager after increasing its target allocation to the asset class in the second quarter.
Dana Emery will relinquish her chair and ceo titles at the end of this year after more than 40 years with the firm.
The plans terminated their mandate with domestic core-plus fixed-income manager Western Asset Management and hired a new record keeper in the fourth quarter.
The oversubscribed fund brings the firm’s total capital under management to approximately $1 billion.
The strategic, minority investment was made through Blackstone’s GP stakes business.