A method for producing a coated steel sheet having a yield strength of at least 800 MPa, a tensile strength of at least 1180 MPa, a total elongation according to ISO standard 6892-1 of at least 13% and a hole expansion ratio HER according to ISO standard 16630:2009 of at least 30%, wherein the method comprises the following successive steps: - providing a cold-rolled steel sheet, made of a steel having a chemical composition containing in weight %: 0.15 % ≤ C ≤ 0.23 % 1.4 % ≤ Mn ≤ 2.6 %, 0.6 % ≤ Si ≤ 1.3 % with C + Si / 10 ≤ 0.30 %, 0.4 % ≤ Al ≤ 1.0%, with Al ≥ 6 C + Mn / 10 − 2.5 %, 0.010 % ≤ Nb ≤ 0.035%, 0.1 % ≤ Mo ≤ 0.5%, the remainder being Fe and unavoidable impurities, - annealing the cold-rolled steel sheet at an annealing temperature T A comprised between 860°C and 900°C, the annealing temperature being lower than Ac3, so as to obtain an annealed steel sheet having a structure consisting of at least 90% of austenite and at least 2% of intercritical ferrite, - quenching the annealed steel sheet from the annealing temperature T A down to a quenching temperature QT comprised between Ms-10°C and Ms-60°C at an average cooling rate Vc higher than 30°C/s, to obtain a quenched sheet, - heating the quenched sheet from the quenching temperature QT to a partitioning temperature PT comprised between 410°C and 470°C, and maintaining the sheet at the partitioning temperature PT for a partitioning time Pt comprised between 60s and 130s, - hot-dip coating the steel sheet in a bath, - cooling the steel sheet down to the room temperature, to obtain a coated steel sheet having a microstructure comprising, in area fraction: - between 45% and 68% of martensite, the martensite consisting of partitioned martensite and fresh martensite, between 85% and 95% of the martensite being partitioned martensite, said partitioned martensite having a C content of at most 0.45%, - between 10% and 15% of retained austenite, - between 2% and 10% of intercritical ferrite, - between 20% and 30% of lower bainite. - providing a cold-rolled steel sheet, made of a steel having a chemical composition containing in weight %: 0.15 % ≤ C ≤ 0.23 % 1.4 % ≤ Mn ≤ 2.6 %, 0.6 % ≤ Si ≤ 1.3 % with C + Si / 10 ≤ 0.30 %, 0.4 % ≤ Al ≤ 1.0%, with Al ≥ 6 C + Mn / 10 − 2.5 %, 0.010 % ≤ Nb ≤ 0.035%, 0.1 % ≤ Mo ≤ 0.5%, the remainder being Fe and unavoidable impurities, - annealing the cold-rolled steel sheet at an annealing temperature T A comprised between 860°C and 900°C, the annealing temperature being lower than Ac3, so as to obtain an annealed steel sheet having a structure consisting of at least 90% of austenite and at least 2% of intercritical ferrite, - quenching the annealed steel sheet from the annealing temperature T A down to a quenching temperature QT comprised between Ms-10°C and Ms-60°C at an average cooling rate Vc higher than 30°C/s, to obtain a quenched sheet, - heating the quenched sheet from the quenching temperature QT to a partitioning temperature PT comprised between 410°C and 470°C, and maintaining the sheet at the partitioning temperature PT for a partitioning time Pt comprised between 60s and 130s, - hot-dip coating the steel sheet in a bath, - cooling the steel sheet down to the room temperature, to obtain a coated steel sheet having a microstructure comprising, in area fraction: - between 45% and 68% of martensite, the martensite consisting of partitioned martensite and fresh martensite, between 85% and 95% of the martensite being partitioned martensite, said partitioned martensite having a C content of at most 0.45%, - between 10% and 15% of retained austenite, - between 2% and 10% of intercritical ferrite, - between 20% and 30% of lower bainite.