A tenfold diffraction pattern has been observed in a rapidly solidified Nb18Fe52alloy by transmission electron microscopy. This tenfold diffraction pattern has many fewer diffraction spots than that of an Al-TM (transition metal) decagonal phase, but tilting experiments through 90° apparently show that it exhibits decagonal symmetry. High-resolution electron microscopy images corresponding to the tenfold diffraction pattern shows that it comes from an a periodic arrangement of icosahedral chains in real space. The structure factors which are calculated according to the ideal model and real model are nearly consistent with the experimental results. It is suggested that this is a new type of decagonal phase closely related to the Zr4Al3, and MgCu2, units of pentagonal Frank-Kasper phases.