This paper introduces a novel passive method and structure designed to mitigate unwanted interference at the antenna in conventional Global Positioning System (GPS) applications. In contrast to traditional approaches that typically utilize high-impedance structures with limited cancellation or antenna arrays employing null-steering techniques, which often result in increased complexity and cost, this study proposes the use of a single-element circularly polarized truncated microstrip patch antenna radially loaded by a magneto-dielectric metamaterial (MTM) structure. The problem is analytically examined, and an appropriate meta cell is chosen, designed, and fabricated. Numerical simulations demonstrate that owing to the magnetic behavior of a new low-profile capacitively-loaded loop (CLL), it serves as an effective structure for suppressing unwanted azimuthal incident plane waves by up to 40 dB. The proposed MTM cover features a cylindrical shape with a diameter and height of 0.27λ0 and 0.42λ0, respectively, achieving a gain and efficiency of 6.5 dBi and 85%, respectively.