Entropy balance and evidence for local spin singlets in a Kagome-like magnet

We have measured the specific heat C(T) of the S = 3/2 Kagome-lattice-containing compound SrCr9pGa12-9pO19. We find little field dependence of the low-temperature C(T), consistent with a low-energy spectrum dominated by many-body singlet excitations. At high temperatures, we recover only similar to 50% of the total R ln4 entropy.