Fused-pentagon is known to result in an increase of local steric strain according to the isolated pentagon rule (IPR), and for all reported non-IPR clusterfullerenes multiple (two or three) metals are required to stabilize the strained fused-pentagons, making it difficult to access the single-atom properties. In this talk, we present the syntheses and isolations of novel non-IPR monometallic clusterfullerenes MNC@C₇₆ (M=Tb, Y), in which one pair of strained fused-pentagon is stabilized by a monometallic cluster. The molecular structures of MNC@C₇₆ (M=Tb, Y) were determined unambiguously by single crystal X-ray diffraction, featuring a non-IPR C_2v(19138)-C₇₆ cage entrapping a nearly linear MNC cluster, which is remarkably different from the triangular MNC cluster within the reported analogous clusterfullerenes based on IPR-obeying C₈₂ cages. In specific, TbNC@C₇₆ molecule is found to be a field-induced single-molecule magnet (SMM).