Experimental Observation of Pentaatomic Tetracoordinate Planar Si- and Ge-Containing Molecules: MAl(4)(-) and MAl(4) The theoretical work was done at Utah State University and supported by the donors of The Petroleum Research Fund (ACS-PRF no. 35255-AC6), administered by the American Chemical Society. The experimental work was supported by the National Science Foundation (DMR-9622733) and was performed at the W. R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by DOE's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory, which is operated for DOE by Battelle Memorial Institute. L.S.W. is an Alfred P. Sloan Foundation Research Fellow. M=Si, Ge.