An antenna (100), which is designed for exciting and/or detecting a magnetic resonance in an object (1) under investigation, comprises a conductor loop (10) with an inner conductor (11) and a primary shield conductor (12), which form at least one waveguide, wherein the primary shield conductor (12) is interrupted by a gap (13), and wherein a secondary shield conductor (14) is provided which surrounds the primary shield conductor (12), wherein a dielectric (15) is arranged between the primary shield conductor (12) and the secondary shield conductor (14) and at least the gap is covered by the secondary shield conductor (14). An antenna arrangement which comprises a plurality of such antennas, a magnetic resonance device, and a method for magnetic resonance imaging or magnetic resonance spectroscopy are also described.