GeC3Ge was previously produced by the dual laser ablation of germanium and carbon rods, and the v(3)(sigma(u)) carbon-carbon stretching fundamental was assigned at 1920.7 cm(-1). This paper presents results from new experiments that have enhanced the production of the molecule via laser ablation of a single sintered germanium- carbon rod, thus enabling the identification of two additional infrared active vibrational fundamentals. Ge participates strongly in one of these, the v(4)(sigma(u)) mode, and the corresponding Ge isotopic shifts reported here are the first for a germanium-carbon species. GeC3Ge was produced by trapping the products from the laser evaporation of the Ge-C rod, in solid Ar at similar to 10 K, and recording the FTIR (Fourier transform infrared) spectra. Comparison of Ge-70,Ge-72,Ge-73,Ge-74,Ge-76 and C-13 isotopic shift measurements with the predictions of density functional theory calculations (DFT) at the B3LYP/cc-pVDZ level confirms the identification of the v(4)(sigma(u)) stretching fundamental at 735.3 cm(-1) and the v(6)(pi(u)) bending fundamental at 580.1 cm(-1) for linear GeC3Ge.