The history of the discovery of superfluidity in helium has two parts.
First, the discovery of superfluidity in liquid helium-4 (a Bose–Einstein condensate) in 1937
by Pyotr Kapitsa, John F. Allen, and Don Misener.
Second, the discovery of superfluidity in helium-3 in the 1970s
by David Lee, Douglas Osheroff, and Robert Richardson.
Unlike helium-4 atoms, which are bosons, helium-3 atoms are fermions,
so the explanation for its superfluidity is completely different.
Bosons have an even number of nucleons;
fermions have an odd number.
For a fermion to become superconducting,
each atom must pair up with another,
resulting in an even number of nucleons.
See also in The book of science:
Readings on wikipedia: