  PbCuTe2O6 is a rare example of a spin liquid candidate featuring a three
dimensional magnetic lattice. Strong geometric frustration arises from the
dominant antiferromagnetic interaction which generates a hyperkagome network of
Cu2+ ions although additional interactions enhance the magnetic lattice
connectivity. Through a combination of magnetization measurements and local
probe investigation by NMR and muSR down to 20 mK, we provide a robust evidence
for the absence of magnetic freezing in the ground state. The local spin
susceptibility probed by the NMR shift hardly deviates from the macroscopic one
down to 1 K pointing to a homogeneous magnetic system with a low defect
concentration. The saturation of the NMR shift and the sublinear power law
temperature (T) evolution of the 1/T1 NMR relaxation rate at low T point to a
non-singlet ground state favoring a gapless fermionic description of the
magnetic excitations. Below 1 K a pronounced slowing down of the spin dynamics
is witnessed, which may signal a reconstruction of spinon Fermi surface.
Nonetheless, the compound remains in a fluctuating spin liquid state down to
the lowest temperature of the present investigation.
