<math><mrow><mi>π</mi><msub><mi>h</mi><mrow><mn>11</mn><mo>/</mo><mn>2</mn></mrow></msub></mrow></math> rotational structure in the neutron-deficient rare-earth nucleus <math><mmultiscripts><mi>Pm</mi><mprescripts/><none/><mn>131</mn></mmultiscripts></math>